Frédéric Kaplan
Professeur associé
frederic.kaplan@epfl.ch +41 21 693 02 53 http://fkaplan.wordpress.com
EPFL CDH DHI DHLAB
INN 141 (Bâtiment INN)
Station 14
CH-1015 Lausanne
EPFL IC-DO
INN 141 (Bâtiment INN)
Station 14
CH-1015 Lausanne
Domaines de compétences
Sur le web
Biographie
Diplômé de l’École Nationale Supérieure des Télécommunications, il a effectué une thèse en intelligence artificielle à l’Université Paris 6 sur la modélisation des dynamiques langagières. Il a ensuite travaillé dix ans au Sony Computer Science Laboratory et pendant six ans dans l’unité de recherche pédagogique de l’EPFL, au Rolex Learning Center.
Frédéric Kaplan est l’auteur de nombreux livres, de plus d’une centaine de publications scientifiques et d’une dizaine de brevets. Ses travaux ont été présentés dans plusieurs musées, notamment au Centre Pompidou à Paris, au Museum of Modern Art à New York, au Grand Palais à Paris et à la Biennale d’Architecture de Venise. Frédéric Kaplan est aussi le fondateur de la société OZWE qui est aujourd’hui un acteur international dans le domaine de la réalité virtuelle.
Publications Infoscience
2019
A deep learning approach to Cadastral Computing
2019-07-11. Digital Humanities Conference, , Utrecht, Netherlands , July 8-12, 2019.
This article presents a fully automatic pipeline to transform the Napoleonic Cadastres into an information system. The cadastres established during the first years of the 19th century cover a large part of Europe. For many cities they give one of the first geometrical surveys, linking precise parcels with identification numbers. These identification numbers points to registers where the names of the proprietary. As the Napoleonic cadastres include millions of parcels , it therefore offers a detailed snapshot of large part of Europe’s population at the beginning of the 19th century. As many kinds of computation can be done on such a large object, we use the neologism “cadastral computing” to refer to the operations performed on such datasets. This approach is the first fully automatic pipeline to transform the Napoleonic Cadastres into an information system.
Search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV in the diphoton final state in proton-proton collisions at $\sqrt{s}=$ 8 and 13 TeV
Physics Letters B. 2019-06-10.
DOI : 10.1016/j.physletb.2019.03.064.
The results of a search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV decaying into two photons are presented. The analysis uses the data set collected with the CMS experiment in proton-proton collisions during the 2012 and 2016 LHC running periods. The data sample corresponds to an integrated luminosity of 19.7 (35.9)fb−1 at s=8 (13) TeV. The expected and observed 95% confidence level upper limits on the product of the cross section and branching fraction into two photons are presented. The observed upper limit for the 2012 (2016) data set ranges from 129 (161) fb to 31 (26) fb. The statistical combination of the results from the analyses of the two data sets in the common mass range between 80 and 110 GeV yields an upper limit on the product of the cross section and branching fraction, normalized to that for a standard model-like Higgs boson, ranging from 0.7 to 0.2, with two notable exceptions: one in the region around the Z boson peak, where the limit rises to 1.1, which may be due to the presence of Drell–Yan dielectron production where electrons could be misidentified as isolated photons, and a second due to an observed excess with respect to the standard model prediction, which is maximal for a mass hypothesis of 95.3 GeV with a local (global) significance of 2.8 (1.3) standard deviations.
Combinations of single-top-quark production cross-section measurements and $|f_{\rm LV}V_{tb}|$ determinations at $\sqrt{s}=7$ and 8 TeV with the ATLAS and CMS experiments
Journal of High Energy Physics. 2019-05-16.
DOI : 10.1007/JHEP05(2019)088.
This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at $ \sqrt{s} $ = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb$^{−1}$ at $ \sqrt{s} $ = 7 TeV and 12.2 to 20.3 fb$^{−1}$ at $ \sqrt{s} $ = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at $ \sqrt{s} $ = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at $ \sqrt{s} $ = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at $ \sqrt{s} $ = 8 TeV. The square of the magnitude of the CKM matrix element V$_{tb}$ multiplied by a form factor f$_{LV}$ is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |V$_{td}$|, |V$_{ts}$| ≪ |V$_{tb}$|. All the |f$_{LV}$V$_{tb}$|$^{2}$ determinations, extracted from individual ratios at $ \sqrt{s} $ = 7 and 8 TeV, are combined, resulting in |f$_{LV}$V$_{tb}$| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.
Measurement of inclusive very forward jet cross sections in proton-lead collisions at $ \sqrt{s_{\mathrm{NN}}} $ = 5.02 TeV
Journal of High Energy Physics. 2019-05-07.
DOI : 10.1007/JHEP05(2019)043.
Measurements of differential cross sections for inclusive very forward jet production in proton-lead collisions as a function of jet energy are presented. The data were collected with the CMS experiment at the LHC in the laboratory pseudorapidity range −6.6 < η < −5.2. Asymmetric beam energies of 4 TeV for protons and 1.58 TeV per nucleon for Pb nuclei were used, corresponding to a center-of-mass energy per nucleon pair of $ \sqrt{s_{\mathrm{NN}}} $ = 5.02 TeV. Collisions with either the proton (p+Pb) or the ion (Pb+p) traveling towards the negative η hemisphere are studied. The jet cross sections are unfolded to stable-particle level cross sections with p$_{T}$ ≳ 3 GeV, and compared to predictions from various Monte Carlo event generators. In addition, the cross section ratio of p+Pb and Pb+p data is presented. The results are discussed in terms of the saturation of gluon densities at low fractional parton momenta. None of the models under consideration describes all the data over the full jet-energy range and for all beam configurations. Discrepancies between the differential cross sections in data and model predictions of more than two orders of magnitude are observed.
Measurement of exclusive $\Upsilon$ photoproduction from protons in pPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV
The European Physical Journal C. 2019-03-26.
DOI : 10.1140/epjc/s10052-019-6774-8.
The exclusive photoproduction of $\mathrm {\Upsilon }\mathrm {(nS)} $ meson states from protons, $\gamma \mathrm {p} \rightarrow \mathrm {\Upsilon }\mathrm {(nS)} \,\mathrm {p}$ (with $\mathrm {n}=1,2,3$ ), is studied in ultraperipheral $\mathrm {p}$ Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{\smash [b]{s_{_{\mathrm {NN}}}}} = 5.02\,\text {TeV} $ . The measurement is performed using the $\mathrm {\Upsilon }\mathrm {(nS)} \rightarrow \mu ^+\mu ^-$ decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6 $\,\text {nb}^{-1}$ . Differential cross sections as functions of the $\mathrm {\Upsilon }\mathrm {(nS)} $ transverse momentum squared $p_{\mathrm {T}} ^2$ , and rapidity y, are presented. The $\mathrm {\Upsilon (1S)}$ photoproduction cross section is extracted in the rapidity range $|y |< 2.2$ , which corresponds to photon–proton centre-of-mass energies in the range $91<W_{\gamma \mathrm {p}} <826\,\text {GeV} $ . The data are compared to theoretical predictions based on perturbative quantum chromodynamics and to previous measurements.
Measurement of prompt $\psi$(2S) production cross sections in proton-lead and proton-proton collisions at $\sqrt{s_{_\mathrm{NN}}}=$ 5.02 TeV
Physics Letters B. 2019-03-10.
DOI : 10.1016/j.physletb.2019.01.058.
Measurements of prompt ψ(2S) meson production cross sections in proton–lead (pPb) and proton–proton (pp) collisions at a nucleon–nucleon center-of-mass energy of sNN=5.02TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb−1 and 28.0 pb−1 , respectively. The nuclear modification factor RpPb is measured for prompt ψ(2S) in the transverse momentum range 4<pT<30GeV/c and the center-of-mass rapidity range −2.4<yCM<1.93 . The results on ψ(2S) RpPb are compared to the corresponding modification factor for prompt J/ψ mesons. The results point to different nuclear effects at play in the production of the excited charmonium state compared to the ground state, in the region of backward rapidity and for pT<10GeV/c .
Measurement of nuclear modification factors of $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) mesons in PbPb collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV
Physics Letters B. 2019-03-10.
DOI : 10.1016/j.physletb.2019.01.006.
The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead–lead (PbPb) and proton–proton (pp) collisions at sNN=5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA , derived from the PbPb-to- pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S))>RAA(ϒ(2S))>RAA(ϒ(3S)) . The suppression of ϒ(1S) is larger than that seen at sNN=2.76TeV , although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT , rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date.
Search for Higgs boson pair production in the $\gamma\gamma\mathrm{b\overline{b}}$ final state in pp collisions at $\sqrt{s}=$ 13 TeV
Physics Letters B. 2019-01-10.
DOI : 10.1016/j.physletb.2018.10.056.
A search is presented for the production of a pair of Higgs bosons, where one decays into two photons and the other one into a bottom quark–antiquark pair. The analysis is performed using proton–proton collision data at s=13TeV recorded in 2016 by the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9fb−1 . The results are in agreement with standard model (SM) predictions. In a search for resonant production, upper limits are set on the cross section for new spin-0 or spin-2 particles. For the SM-like nonresonant production hypothesis, the data exclude a product of cross section and branching fraction larger than 2.0fb at 95% confidence level (CL), corresponding to about 24 times the SM prediction. Values of the effective Higgs boson self-coupling κλ are constrained to be within the range −11<κλ<17 at 95% CL, assuming all other Higgs boson couplings are at their SM value. The constraints on κλ are the most restrictive to date.
Search for heavy resonances decaying into two Higgs bosons or into a Higgs boson and a W or Z boson in proton-proton collisions at 13 TeV
Journal of High Energy Physics. 2019-01-07.
DOI : 10.1007/JHEP01(2019)051.
A search is presented for massive narrow resonances decaying either into two Higgs bosons, or into a Higgs boson and a W or Z boson. The decay channels considered are $ \mathrm{H}\mathrm{H}\to \mathrm{b}\overline{\mathrm{b}}{\tau}^{+}{\tau}^{-} $ and $ \mathrm{V}\mathrm{H}\to \mathrm{q}\overline{\mathrm{q}}{\tau}^{+}{\tau}^{-} $ , where H denotes the Higgs boson, and V denotes the W or Z boson. This analysis is based on a data sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV by the CMS Collaboration, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. For the TeV-scale mass resonances considered, substructure techniques provide ways to differentiate among the hadronization products from vector boson decays to quarks, Higgs boson decays to bottom quarks, and quark- or gluon-induced jets. Reconstruction techniques are used that have been specifically optimized to select events in which the tau lepton pair is highly boosted. The observed data are consistent with standard model expectations and upper limits are set at 95% confidence level on the product of cross section and branching fraction for resonance masses between 0.9 and 4.0 TeV. Exclusion limits are set in the context of bulk radion and graviton models:spin-0 radion resonances are excluded below a mass of 2.7 TeV at 95% confidence level. In the spin-1 heavy vector triplet framework, mass-degenerate W′ and Z′ resonances with dominant couplings to the standard model gauge bosons are excluded below a mass of 2.8 TeV at 95% confidence level. These are the first limits for massive resonances at the TeV scale with these decay channels at $ \sqrt{s}=13 $ TeV.
2018
Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at $\sqrt{s_{NN}}=$ 5.02 TeV Using Isolated Photon-Tagged Jets
Physical Review Letters. 2018-12-15.
DOI : 10.1103/PhysRevLett.121.242301.
Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with pTjet>30 GeV/c in events containing an isolated photon with pTγ>60 GeV/c, using charged tracks with transverse momentum pTtrk>1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial pT and azimuthal angle of the parton whose shower produced the jet. For central Pb-Pb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central Pb-Pb events show an excess (depletion) of low (high) pT particles, with a transition around 3 GeV/c. This measurement shows for the first time the in-medium shower modifications of partons (quark dominated) with well-defined initial kinematics. It constitutes a new well-controlled reference for testing theoretical models of the parton passage through the quark-gluon plasma.
Informatica per Umanisti: da Venezia al mondo intero attraverso l’Europa
Conferenza per la Società Dante Alighieri, University of Bern, Switzerland, December 10, 2018.
In un momento di apertura del mondo scientifico verso un pubblico più ampio, questa conferenza vuole essere una facile introduzione alle digital humanities. L’argomento del conferenza è infatti l’informatica per umanisti, un nuovo ambito di ricerca che arricchisce le discipline umanistiche attraverso l’uso di nuove tecnologie. La mia esperienza personale sarà il filo conduttore di questa introduzione e la conferenza sarà l’occasione per parlare dei progetti ai quali ho contribuito nel corso degli ultimi cinque anni. Da Parigi a Venezia, da Losanna a Boston, fare ricerca vuol dire fare esperienze in tutto il mondo. Parlerò di Bruno Latour e dei suoi modi d’esistenza, di Frédéric Kaplan e della sua macchina del tempo, di Franco Moretti e della sua lettura a distanza, e di Marilyne Andersen e della sua cartografia delle affinità, tutte persone che ho avuto il piacere di incontrare e hanno arricchito il mio percorso accademico. Attraverso un racconto visuale fatto di immagini e video, vi spiegherò come le Digital Humanities possono rendere archivi, musei e biblioteche luoghi più interessanti per tutti.
Measurements of Higgs boson properties in the diphoton decay channel in proton-proton collisions at $\sqrt{s} =$ 13 TeV
Journal of High Energy Physics. 2018-11-29.
DOI : 10.1007/JHEP11(2018)185.
Measurements of Higgs boson properties in the H → γγ decay channel are reported. The analysis is based on data collected by the CMS experiment in proton-proton collisions at $ \sqrt{s}=13 $ TeV during the 2016 LHC running period, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. Allowing the Higgs mass to float, the measurement yields a signal strength relative to the standard model prediction of 1.18$_{− 0.14}^{+ 0.17}$ = 1.18$_{− 0.11}^{+ 0.12}$ (stat)$_{− 0.07}^{+ 0.09}$ (syst)$_{− 0.06}^{+ 0.07}$ (theo), which is largely insensitive to the exact Higgs mass around 125 GeV. Signal strengths associated with the different Higgs boson production mechanisms, couplings to bosons and fermions, and effective couplings to photons and gluons are also measured.
Measurement of differential cross sections for Z boson production in association with jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV
The European Physical Journal C. 2018-11-22.
DOI : 10.1140/epjc/s10052-018-6373-0.
The production of a ${\text {Z}}$ boson, decaying to two charged leptons, in association with jets in proton-proton collisions at a centre-of-mass energy of 13 $\,\text {TeV}$ is measured. Data recorded with the CMS detector at the LHC are used that correspond to an integrated luminosity of 2.19 $\,\text {fb}^\text {-1}$ . The cross section is measured as a function of the jet multiplicity and its dependence on the transverse momentum of the ${\text {Z}}$ boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, which quantifies the hadronic activity, and the balance in transverse momentum between the reconstructed jet recoil and the ${\text {Z}}$ boson. The measurements are compared with predictions from four different calculations. The first two merge matrix elements with different parton multiplicities in the final state and parton showering, one of which includes one-loop corrections. The third is a fixed-order calculation with next-to-next-to-leading order accuracy for the process with a ${\text {Z}}$ boson and one parton in the final state. The fourth combines the fully differential next-to-next-to-leading order calculation of the process with no parton in the final state with next-to-next-to-leading logarithm resummation and parton showering.
Measurement of the top quark mass with lepton+jets final states using $\mathrm {p}$ $\mathrm {p}$ collisions at $\sqrt{s}=13\,\text {TeV} $
The European Physical Journal C. 2018-11-02.
DOI : 10.1140/epjc/s10052-018-6332-9.
The mass of the top quark is measured using a sample of ${{\text {t}}\overline{{\text {t}}}}$ events collected by the CMS detector using proton-proton collisions at $\sqrt{s}=13$ $\,\text {TeV}$ at the CERN LHC. Events are selected with one isolated muon or electron and at least four jets from data corresponding to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ . For each event the mass is reconstructed from a kinematic fit of the decay products to a ${{\text {t}}\overline{{\text {t}}}}$ hypothesis. Using the ideogram method, the top quark mass is determined simultaneously with an overall jet energy scale factor (JSF), constrained by the mass of the W boson in ${\text {q}} \overline{{\text {q}}} ^\prime $ decays. The measurement is calibrated on samples simulated at next-to-leading order matched to a leading-order parton shower. The top quark mass is found to be $172.25 \pm 0.08\,\text {(stat+JSF)} \pm 0.62\,\text {(syst)} \,\text {GeV} $ . The dependence of this result on the kinematic properties of the event is studied and compared to predictions of different models of ${{\text {t}}\overline{{\text {t}}}}$ production, and no indications of a bias in the measurements are observed.
Measurement of the production cross section for single top quarks in association with W bosons in proton-proton collisions at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-10-18.
DOI : 10.1007/JHEP10(2018)117.
A measurement is presented of the associated production of a single top quark and a W boson in proton-proton collisions at $ \sqrt{s}=13 $ TeV by the CMS Collaboration at the CERN LHC. The data collected corresponds to an integrated luminosity of 35.9 fb$^{−1}$. The measurement is performed using events with one electron and one muon in the final state along with at least one jet originated from a bottom quark. A multivariate discriminant, exploiting the kinematic properties of the events, is used to separate the signal from the dominant $ \mathrm{t}\overline{\mathrm{t}} $ background. The measured cross section of 63.1 ± 1.8(stat) ± 6.4(syst) ± 2.1 (lumi) pb is in agreement with the standard model expectation.
Search for new physics in dijet angular distributions using proton–proton collisions at $\sqrt{s}=$ 13 TeV and constraints on dark matter and other models
The European Physical Journal C. 2018-09-28.
DOI : 10.1140/epjc/s10052-018-6242-x.
A search is presented for physics beyond the standard model, based on measurements of dijet angular distributions in proton–proton collisions at $\sqrt{s}=13\hbox {TeV}$ . The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ . The observed distributions, corrected to particle level, are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Constraints are placed on models containing quark contact interactions, extra spatial dimensions, quantum black holes, or dark matter, using the detector-level distributions. In a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 or 17.5TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani–Hamed–Dimopoulos–Dvali model of extra dimensions. In the Giudice–Rattazzi–Wells convention, the cutoff scale is excluded up to 10.1TeV. The production of quantum black holes is excluded for masses below 5.9 and 8.2TeV, depending on the model. For the first time, lower limits between 2.0 and 4.6TeVare set on the mass of a dark matter mediator for (axial-)vector mediators, for the universal quark coupling $g_{\mathrm {\mathrm {q}}} =1.0$ .
Search for a heavy resonance decaying into a Z boson and a Z or W boson in 2ℓ2q final states at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-09-18.
DOI : 10.1007/JHEP09(2018)101.
A search has been performed for heavy resonances decaying to ZZ or ZW in 2ℓ2q final states, with two charged leptons (ℓ = e, μ) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of $ \sqrt{s}=13 $ TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W$^{′}$ bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.
Measurement of the $\mathrm{Z}\gamma^{*} \to \tau\tau$ cross section in pp collisions at $\sqrt{s} = $ 13 TeV and validation of $\tau$ lepton analysis techniques
The European Physical Journal C. 2018-09-03.
DOI : 10.1140/epjc/s10052-018-6146-9.
A measurement is presented of the $\mathrm {Z}/\gamma ^{*} \rightarrow \tau \tau $ cross section in $\text {pp}$ collisions at $\sqrt{s} = 13\hbox { TeV}$ , using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of $2.3\hbox { fb}^{-1}$ . The product of the inclusive cross section and branching fraction is measured to be $\sigma (\text {pp} \rightarrow \mathrm {Z}/\gamma ^{*}\text {+X}) \, \mathcal {B}(\mathrm {Z}/\gamma ^{*} \rightarrow \tau \tau ) = 1848 \pm 12\,(\text {stat}) \pm 67\text { (syst \,+\,lumi)}\text { pb} $ , in agreement with the standard model expectation, computed at next-to-next-to-leading order accuracy in perturbative quantum chromodynamics. The measurement is used to validate new analysis techniques relevant for future measurements of $\tau $ lepton production. The measurement also provides the reconstruction efficiency and energy scale for $\tau $ decays to hadrons $\,+\,\nu _{\tau }$ final states, determined with respective relative uncertainties of 2.2 and 0.9%.
Search for additional neutral MSSM Higgs bosons in the $\tau\tau$ final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2018-09-03.
DOI : 10.1007/JHEP09(2018)007.
A search is presented for additional neutral Higgs bosons in the τ τ final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the m$_{h}^{hod +}$ scenario these limits translate into a 95% CL exclusion of tan β > 6 for neutral Higgs boson masses below 250 GeV, where tan β is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tan β = 60.
Search for resonant pair production of Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at 13 TeV
Journal of High Energy Physics. 2018-08-23.
DOI : 10.1007/JHEP08(2018)152.
A search for a narrow-width resonance decaying into two Higgs bosons, each decaying into a bottom quark-antiquark pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 35.9 fb$^{−1}$ at $ \sqrt{s}=13 $ TeV recorded by the CMS detector at the LHC. No evidence for such a signal is observed. Upper limits are set on the product of the production cross section for the resonance and the branching fraction for the selected decay mode in the resonance mass range from 260 to 1200 GeV.
Search for narrow and broad dijet resonances in proton-proton collisions at $ \sqrt{s}=13 $ TeV and constraints on dark matter mediators and other new particles
Journal of High Energy Physics. 2018-08-21.
DOI : 10.1007/JHEP08(2018)130.
Searches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at $ \sqrt{s}=13 $ TeV corresponding to an integrated luminosity of up to 36 fb$^{−1}$. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W$^{′}$ bosons below 3.3 TeV, Z$^{′}$ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.
Search for $R$-parity violating supersymmetry in pp collisions at $\sqrt{s} = $ 13 TeV using b jets in a final state with a single lepton, many jets, and high sum of large-radius jet masses
Physics Letters B. 2018-08-10.
DOI : 10.1016/j.physletb.2018.06.028.
Results are reported from a search for physics beyond the standard model in proton–proton collisions at a center-of-mass energy of s=13TeV . The search uses a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event. The data sample corresponds to an integrated luminosity of 35.9 fb −1 recorded by the CMS experiment at the LHC. No significant excess beyond the prediction from standard model processes is observed. The results are interpreted in terms of upper limits on the production cross section for R -parity violating supersymmetric extensions of the standard model using a benchmark model of gluino pair production, in which each gluino decays promptly via g˜→tbs . Gluinos with a mass below 1610 GeV are excluded at 95% confidence level.
dhSegment : A generic deep-learning approach for document segmentation
The 16th International Conference on Frontiers in Handwriting Recognition, Niagara Falls, USA, 5-8 August 2018.
Comparing human and machine performances in transcribing 18th century handwritten Venetian script
2018-07-26. Digital Humanities Conference , Mexico City, Mexico , June 24-29, 2018.
Automatic transcription of handwritten texts has made important progress in the recent years. This increase in performance, essentially due to new architectures combining convolutional neural networks with recurrent neutral networks, opens new avenues for searching in large databases of archival and library records. This paper reports on our recent progress in making million digitized Venetian documents searchable, focusing on a first subset of 18th century fiscal documents from the Venetian State Archives. For this study, about 23’000 image segments containing 55’000 Venetian names of persons and places were manually transcribed by archivists, trained to read such kind of handwritten script. This annotated dataset was used to train and test a deep learning architecture with a performance level (about 10% character error rate) that is satisfactory for search use cases. This paper compares this level of reading performance with the reading capabilities of Italian-speaking transcribers. More than 8500 new human transcriptions were produced, confirming that the amateur transcribers were not as good as the expert. However, on average, the machine outperforms the amateur transcribers in this transcription tasks.
Measurement of the inelastic proton-proton cross section at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-07-25.
DOI : 10.1007/JHEP07(2018)161.
A measurement of the inelastic proton-proton cross section with the CMS detector at a center-of-mass energy of $ \sqrt{s}=13 $ TeV is presented. The analysis is based on events with energy deposits in the forward calorimeters, which cover pseudorapidities of −6.6 < η < −3.0 and +3.0 < η < +5.2. An inelastic cross section of 68.6 ± 0.5(syst) ± 1.6(lumi) mb is obtained for events with M$_{X}$ > 4.1 GeV and/or M$_{Y}$ > 13 GeV, where M$_{X}$ and M$_{Y}$ are the masses of the diffractive dissociation systems at negative and positive pseudorapidities, respectively. The results are compared with those from other experiments as well as to predictions from high-energy hadron-hadron interaction models.
Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13 TeV with the CMS-TOTEM precision proton spectrometer
Journal of High Energy Physics. 2018-07-24.
DOI : 10.1007/JHEP07(2018)153.
The process pp → pℓ$^{+}$ℓ$^{−}$p$^{(*)}$, with ℓ$^{+}$ℓ$^{−}$ a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $ \sqrt{s}=13 $ TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p$^{*}$, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb$^{−1}$ collected during standard, high-luminosity LHC operation. A total of 12 μ$^{+}$μ$^{−}$ and 8 e$^{+}$e$^{−}$ pairs with m(ℓ$^{+}$ℓ$^{−}$) > 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 ± 0.07 (stat) ± 0.53 (syst) and 2.36 ± 0.09 (stat) ± 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged γγ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.
Electroweak production of two jets in association with a Z boson in proton–proton collisions at $\sqrt{s}= $ 13 $\,\text {TeV}$
The European Physical Journal C. 2018-07-20.
DOI : 10.1140/epjc/s10052-018-6049-9.
A measurement of the electroweak (EW) production of two jets in association with a $\mathrm {Z} $ boson in proton-proton collisions at $\sqrt{s}=13\,\text {TeV} $ is presented, based on data recorded in 2016 by the CMS experiment at the LHC corresponding to an integrated luminosity of 35.9 $\,\text {fb}^{\text {--}1}$ . The measurement is performed in the $\ell \ell \mathrm {jj}$ final state with $\ell $ including electrons and muons, and the jets j corresponding to the quarks produced in the hard interaction. The measured cross section in a kinematic region defined by invariant masses $m_{\ell \ell } >50\,\text {GeV} $ , $m_{\mathrm {jj}} >120\,\text {GeV} $ , and transverse momenta $p_{\mathrm {T j}} > 25\,\text {GeV}$ is $\sigma _\mathrm {EW}(\ell \ell \mathrm {jj})= 534 \pm 20\,\text {(stat)} \pm 57\,\text {(syst) fb} $ , in agreement with leading-order standard model predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. No evidence is found and limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are $-2.6< c_{WWW}/\varLambda ^2 < 2.6\,\text {TeV}^{-2}$ and $-8.4< c_{W}/\varLambda ^2 < 10.1\,\text {TeV}^{-2}$ . The additional jet activity of events in a signal-enriched region is also studied, and the measurements are in agreement with predictions.
Search for a heavy resonance decaying into a Z boson and a vector boson in the $ \nu \overline{\nu}\mathrm{q}\overline{\mathrm{q}} $ final state
Journal of High Energy Physics. 2018-07-11.
DOI : 10.1007/JHEP07(2018)075.
A search is presented for a heavy resonance decaying into either a pair of Z bosons or a Z boson and a W boson (ZZ or WZ), with a Z boson decaying into a pair of neutrinos and the other boson decaying hadronically into two collimated quarks that are reconstructed as a highly energetic large-cone jet. The search is performed using the data collected with the CMS detector at the CERN LHC during 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to a total integrated luminosity of 35.9 fb$^{−1}$. No excess is observed in data with regard to background expectations. Results are interpreted in scenarios of physics beyond the standard model. Limits at 95% confidence level on production cross sections are set at 0.9 fb (63 fb) for spin-1 W′ bosons, included in the heavy vector triplet model, with mass 4.0 TeV (1.0 TeV), and at 0.5 fb (40 fb) for spin-2 bulk gravitons with mass 4.0 TeV (1.0 TeV). Lower limits are set on the masses of W′ bosons in the context of two versions of the heavy vector triplet model of 3.1TeV and 3.4 TeV, respectively.
The Scholar Index: Towards a Collaborative Citation Index for the Arts and Humanities
Mexico City, 26-29 June 2018.
Search for high-mass resonances in final states with a lepton and missing transverse momentum at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-06-25.
DOI : 10.1007/JHEP06(2018)128.
A search for new high-mass resonances in proton-proton collisions having final states with an electron or muon and missing transverse momentum is presented. The analysis uses proton-proton collision data collected in 2016 with the CMS detector at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The transverse mass distribution of the charged lepton-neutrino system is used as the discriminating variable. No significant deviation from the standard model prediction is found. The best limit, from the combination of electron and muon channels, is 5.2 TeV at 95% confidence level for the mass of a W′ boson with the same couplings as those of the standard model W boson. Exclusion limits of 2.9 TeV are set on the inverse radius of the extra dimension in the framework of split universal extra dimensions. In addition, model-independent limits are set on the production cross section and coupling strength of W′ bosons decaying into this final state. An interpretation is also made in the context of an R parity violating supersymmetric model with a slepton as a mediator and flavor violating decay.
Search for a new scalar resonance decaying to a pair of Z bosons in proton-proton collisions at $\sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-06-25.
DOI : 10.1007/JHEP06(2018)127.
A search for a new scalar resonance decaying to a pair of Z bosons is performed in the mass range from 130 GeV to 3 TeV, and for various width scenarios. The analysis is based on proton-proton collisions recorded by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{−1}$ at a center-of-mass energy of 13 TeV. The Z boson pair decays are reconstructed using the 4ℓ, 2ℓ2q, and 2ℓ2ν final states, where ℓ = e or μ. Both gluon fusion and electroweak production of the scalar resonance are considered, with a free parameter describing their relative cross sections. A dedicated categorization of events, based on the kinematic properties of associated jets, and matrix element techniques are employed for an optimal signal and background separation. A description of the interference between signal and background amplitudes for a resonance of an arbitrary width is included. No significant excess of events with respect to the standard model expectation is observed and limits are set on the product of the cross section for a new scalar boson and the branching fraction for its decay to ZZ for a large range of masses and widths.
Search for $\mathrm{t}\overline{\mathrm{t}}$H production in the all-jet final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2018-06-20.
DOI : 10.1007/JHEP06(2018)101.
A search is presented for the associated production of a Higgs boson with a top quark pair in the all-jet final state. Events containing seven or more jets are selected from a sample of proton-proton collisions at $ \sqrt{s}=13 $ TeV collected with the CMS detector at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. To separate the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ signal from the irreducible $ \mathrm{t}\overline{\mathrm{t}}+\mathrm{b}\overline{\mathrm{b}} $ background, the analysis assigns leading order matrix element signal and background probability densities to each event. A likelihood-ratio statistic based on these probability densities is used to extract the signal. The results are provided in terms of an observed ttH signal strength relative to the standard model production cross section μ = σ/σ$_{SM}$, assuming a Higgs boson mass of 125 GeV. The best fit value is $ \widehat{\mu}=0.9\pm 0.7\left(\mathrm{stat}\right)\pm 1.3\left(\mathrm{syst}\right)=0.9\pm 1.5\left(\mathrm{tot}\right) $ , and the observed and expected upper limits are, respectively, μ < 3.8 and < 3.1 at 95% confidence levels.
Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $\sqrt{s}=$ 13 TeV
Journal of Instrumentation. 2018-06-19.
DOI : 10.1088/1748-0221/13/06/P06015.
The CMS muon detector system, muon reconstruction software, and high-level trigger underwent significant changes in 2013–2014 in preparation for running at higher LHC collision energy and instantaneous luminosity. The performance of the modified system is studied using proton-proton collision data at center-of-mass energy √s=13 TeV, collected at the LHC in 2015 and 2016. The measured performance parameters, including spatial resolution, efficiency, and timing, are found to meet all design specifications and are well reproduced by simulation. Despite the more challenging running conditions, the modified muon system is found to perform as well as, and in many aspects better than, previously. We dedicate this paper to the memory of Prof. Alberto Benvenuti, whose work was fundamental for the CMS muon detector.
Measurement of differential cross sections for the production of top quark pairs and of additional jets in lepton+jets events from pp collisions at $\sqrt{s} =$ 13 TeV
Physical Review D. 2018-06-16.
DOI : 10.1103/PhysRevD.97.112003.
Differential and double-differential cross sections for the production of top quark pairs in proton-proton collisions at s=13 TeV are measured as a function of kinematic variables of the top quarks and the top quark-antiquark (tt¯) system. In addition, kinematic variables and multiplicities of jets associated with the tt¯ production are measured. This analysis is based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.8 fb-1. The measurements are performed in the lepton+jets decay channels with a single muon or electron and jets in the final state. The differential cross sections are presented at the particle level, within a phase space close to the experimental acceptance, and at the parton level in the full phase space. The results are compared to several standard model predictions that use different methods and approximations. The kinematic variables of the top quarks and the tt¯ system are reasonably described in general, though none predict all the measured distributions. In particular, the transverse momentum distribution of the top quarks is more steeply falling than predicted. The kinematic distributions and multiplicities of jets are adequately modeled by certain combinations of next-to-leading-order calculations and parton shower models.
Search for Physics Beyond the Standard Model in Events with High-Momentum Higgs Bosons and Missing Transverse Momentum in Proton-Proton Collisions at 13 TeV
Physical Review Letters. 2018-06-12.
DOI : 10.1103/PhysRevLett.120.241801.
A search for physics beyond the standard model in events with one or more high-momentum Higgs bosons, H, decaying to pairs of b quarks in association with missing transverse momentum is presented. The data, corresponding to an integrated luminosity of 35.9 fb-1, were collected with the CMS detector at the LHC in proton-proton collisions at the center-of-mass energy s=13 TeV. The analysis utilizes a new b quark tagging technique based on jet substructure to identify jets from H→bb¯. Events are categorized by the multiplicity of H-tagged jets, jet mass, and the missing transverse momentum. No significant deviation from standard model expectations is observed. In the context of supersymmetry (SUSY), limits on the cross sections of pair-produced gluinos are set, assuming that gluinos decay to quark pairs, H (or Z), and the lightest SUSY particle, LSP, through an intermediate next-to-lightest SUSY particle, NLSP. With large mass splitting between the NLSP and LSP, and 100% NLSP branching fraction to H, the lower limit on the gluino mass is found to be 2010 GeV.
Search for single production of vector-like quarks decaying to a b quark and a Higgs boson
Journal of High Energy Physics. 2018-06-05.
DOI : 10.1007/JHEP06(2018)031.
A search is presented for single production of heavy vector-like quarks (B) that decay to a Higgs boson and a b quark, with the Higgs boson decaying to a highly boosted $ \mathrm{b}\overline{\mathrm{b}} $ pair reconstructed as a single collimated jet. The analysis is based on data collected by the CMS experiment in proton-proton collisions at $ \sqrt{s}=13 $ TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The data are consistent with background expectations, and upper limits at 95% confidence level on the product of the B quark cross section and the branching fraction are obtained in the range 1.28–0.07 pb, for a narrow B quark with a mass between 700 and 1800 GeV. The production of B quarks with widths of 10, 20 and 30% of the resonance mass is also considered, and the sensitivities obtained are similar to those achieved in the narrow width case. This is the first search at the CERN LHC for the single production of a B quark through its fully hadronic decay channel, and the first study considering finite resonance widths of the B quark.
Measurements of differential cross sections of top quark pair production as a function of kinematic event variables in proton-proton collisions at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-06-01.
DOI : 10.1007/JHEP06(2018)002.
Measurements of differential $ \mathrm{t}\overline{\mathrm{t}} $ production cross sections are presented in the single-lepton decay channel, as a function of a number of kinematic event variables. The measurements are performed with proton-proton collision data at $ \sqrt{s}=13 $ TeV, collected by the CMS experiment at the LHC during 2016, with an integrated luminosity of 35.9 fb$^{−1}$. The data are compared to a variety of state-of-the-art leading-order and next-to-leading-order $ \mathrm{t}\overline{\mathrm{t}} $ simulations.
Search for heavy neutral leptons in events with three charged leptons in proton-proton collisions at $\sqrt{s} =$ 13 TeV
Physical Review Letters. 2018-05-30.
DOI : 10.1103/PhysRevLett.120.221801.
A search for a heavy neutral lepton N of Majorana nature decaying into a W boson and a charged lepton is performed using the CMS detector at the LHC. The targeted signature consists of three prompt charged leptons in any flavor combination of electrons and muons. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV, with an integrated luminosity of 35.9 fb-1. The search is performed in the N mass range between 1 GeV and 1.2 TeV. The data are found to be consistent with the expected standard model background. Upper limits are set on the values of |VeN|2 and |VμN|2, where VℓN is the matrix element describing the mixing of N with the standard model neutrino of flavor ℓ. These are the first direct limits for N masses above 500 GeV and the first limits obtained at a hadron collider for N masses below 40 GeV.
Deep Learning for Logic Optimization Algorithms, 2018 IEEE International Symposium on Circuits and Systems (ISCAS)
2018-05-27. 2018 IEEE International Symposium on Circuits and Systems (ISCAS) , Florence, Italy , May 27-30, 2018. p. 1-4.
DOI : 10.1109/ISCAS.2018.8351885.
The slowing down of Moore's law and the emergence of new technologies puts an increasing pressure on the field of EDA. There is a constant need to improve optimization algorithms. However, finding and implementing such algorithms is a difficult task, especially with the novel logic primitives and potentially unconventional requirements of emerging technologies. In this paper, we cast logic optimization as a deterministic Markov decision process (MDP). We then take advantage of recent advances in deep reinforcement learning to build a system that learns how to navigate this process. Our design has a number of desirable properties. It is autonomous because it learns automatically and does not require human intervention. It generalizes to large functions after training on small examples. Additionally, it intrinsically supports both single- and multi-output functions, without the need to handle special cases. Finally, it is generic because the same algorithm can be used to achieve different optimization objectives, e.g., size and depth.
Search for new physics in events with two soft oppositely charged leptons and missing transverse momentum in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Physics Letters B. 2018-05-25.
DOI : 10.1016/j.physletb.2018.05.062.
A search is presented for new physics in events with two low-momentum, oppositely charged leptons (electrons or muons) and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data collected using the CMS detector at the LHC correspond to an integrated luminosity of 35.9 fb−1 . The observed event yields are consistent with the expectations from the standard model. The results are interpreted in terms of pair production of charginos and neutralinos ( χ˜1± and χ˜20 ) with nearly degenerate masses, as expected in natural supersymmetry models with light higgsinos, as well as in terms of the pair production of top squarks ( t˜ ), when the lightest neutralino and the top squark have similar masses. At 95% confidence level, wino-like χ˜1±/χ˜20 masses are excluded up to 230 GeV for a mass difference of 20 GeV relative to the lightest neutralino. In the higgsino-like model, masses are excluded up to 168 GeV for the same mass difference. For t˜ pair production, top squark masses up to 450 GeV are excluded for a mass difference of 40 GeV relative to the lightest neutralino.
Search for a heavy right-handed W boson and a heavy neutrino in events with two same-flavor leptons and two jets at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2018-05-24.
DOI : 10.1007/JHEP05(2018)148.
A search for a heavy right-handed W boson (W$_{R}$) decaying to a heavy right-handed neutrino and a charged lepton in events with two same-flavor leptons (e or μ) and two jets, is presented. The analysis is based on proton-proton collision data, collected by the CMS Collaboration at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb$^{−1}$. No significant excess above the standard model expectation is seen in the invariant mass distribution of the dilepton plus dijet system. Assuming that couplings are identical to those of the standard model, and that only one heavy neutrino flavor N$_{R}$ contributes significantly to the W$_{R}$ decay width, the region in the two-dimensional $ \left({m}_{{\mathrm{W}}_{\mathrm{R}}},{m}_{{\mathrm{N}}_{\mathrm{R}}}\right) $ mass plane excluded at 95% confidence level extends to approximately $ {m}_{{\mathrm{W}}_{\mathrm{R}}}=4.4 $ TeV and covers a large range of right-handed neutrino masses below the W$_{R}$ boson mass. This analysis provides the most stringent limits on the W$_{R}$ mass to date.
Search for new physics in final states with an energetic jet or a hadronically decaying $W$ or $Z$ boson and transverse momentum imbalance at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$
Physical Review D. 2018-05-22.
DOI : 10.1103/PhysRevD.97.092005.
A search for new physics using events containing an imbalance in transverse momentum and one or more energetic jets arising from initial-state radiation or the hadronic decay of W or Z bosons is presented. A data sample of proton-proton collisions at s=13 TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb-1, is used. The observed data are found to be in agreement with the expectation from standard model processes. The results are interpreted as limits on the dark matter production cross section in simplified models with vector, axial-vector, scalar, and pseudoscalar mediators. Interpretations in the context of fermion portal and nonthermal dark matter models are also provided. In addition, the results are interpreted in terms of invisible decays of the Higgs boson and set stringent limits on the fundamental Planck scale in the Arkani-Hamed, Dimopoulos, and Dvali model with large extra spatial dimensions.
Search for decays of stopped exotic long-lived particles produced in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2018-05-21.
DOI : 10.1007/JHEP05(2018)127.
A search is presented for the decays of heavy exotic long-lived particles (LLPs) that are produced in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC and come to rest in the CMS detector. Their decays would be visible during periods of time well separated from proton-proton collisions. Two decay scenarios of stopped LLPs are explored: a hadronic decay detected in the calorimeter and a decay into muons detected in the muon system. The calorimeter (muon) search covers a period of sensitivity totaling 721 (744) hours in 38.6 (39.0) fb$^{−1}$ of data collected by the CMS detector in 2015 and 2016. The results are interpreted in several scenarios that predict LLPs. Production cross section limits are set as a function of the mean proper lifetime and the mass of the LLPs, for lifetimes between 100 ns and 10 days. These are the most stringent limits to date on the mass of hadronically decaying stopped LLPs, and this is the first search at the LHC for stopped LLPs that decay to muons.
Search for narrow resonances in the b-tagged dijet mass spectrum in proton-proton collisions at $\sqrt{s} =$ 8 TeV
Physical Review Letters. 2018-05-15.
DOI : 10.1103/PhysRevLett.120.201801.
A search for narrow resonances decaying to bottom quark-antiquark pairs is presented, using a data sample of proton-proton collisions at s=8 TeV corresponding to an integrated luminosity of 19.7 fb-1. The search is extended to masses lower than those reached in typical searches for resonances decaying into jet pairs at the LHC, by taking advantage of triggers that identify jets originating from bottom quarks. No significant excess of events is observed above the background predictions. Limits are set on the product of cross section and branching fraction to bottom quarks for spin 0, 1, and 2 resonances in the mass range of 325–1200 GeV. These results improve on the limits for resonances decaying into jet pairs in the 325–500 GeV mass range.
Search for a heavy resonance decaying to a pair of vector bosons in the lepton plus merged jet final state at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-05-15.
DOI : 10.1007/JHEP05(2018)088.
A search for a new heavy particle decaying to a pair of vector bosons (WW or WZ) is presented using data from the CMS detector corresponding to an integrated luminosity of 35.9 fb$^{−1}$ collected in proton-proton collisions at a centre-of-mass energy of 13 TeV in 2016. One of the bosons is required to be a W boson decaying to eν or μν, while the other boson is required to be reconstructed as a single massive jet with substructure compatible with that of a highly-energetic quark pair from a W or Z boson decay. The search is performed in the resonance mass range between 1.0 and 4.4 TeV. The largest deviation from the background-only hypothesis is observed for a mass near 1.4 TeV and corresponds to a local significance of 2.5 standard deviations. The result is interpreted as an upper bound on the resonance production cross section. Comparing the excluded cross section values and the expectations from theoretical calculations in the bulk graviton and heavy vector triplet models, spin-2 WW resonances with mass smaller than 1.07 TeV and spin-1 WZ resonances lighter than 3.05 TeV, respectively, are excluded at 95% confidence level.
Search for natural and split supersymmetry in proton-proton collisions at $ \sqrt{s}=13 $ TeV in final states with jets and missing transverse momentum
Journal of High Energy Physics. 2018-05-04.
DOI : 10.1007/JHEP05(2018)025.
A search for supersymmetry (SUSY) is performed in final states comprising one or more jets and missing transverse momentum using data from proton-proton collisions at a centre-of-mass energy of 13 TeV. The data were recorded with the CMS detector at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb$^{−1}$. The number of signal events is found to agree with the expected background yields from standard model processes. The results are interpreted in the context of simplified models of SUSY that assume the production of gluino or squark pairs and their prompt decay to quarks and the lightest neutralino. The masses of bottom, top, and mass-degenerate light-flavour squarks are probed up to 1050, 1000, and 1325 GeV, respectively. The gluino mass is probed up to 1900, 1650, and 1650 GeV when the gluino decays via virtual states of the aforementioned squarks. The strongest mass bounds on the neutralinos from gluino and squark decays are 1150 and 575 GeV, respectively. The search also provides sensitivity to simplified models inspired by split SUSY that involve the production and decay of long-lived gluinos. Values of the proper decay length cτ$_{0}$ from 10$^{−3}$ to 10$^{5}$ mm are considered, as well as a metastable gluino scenario. Gluino masses up to 1750 and 900 GeV are probed for cτ$_{0}$ = 1 mm and for the metastable state, respectively. The sensitivity is moderately dependent on model assumptions for cτ$_{0}$ ≳ 1 m. The search provides coverage of the cτ$_{0}$ parameter space for models involving long-lived gluinos that is complementary to existing techniques at the LHC.
Jet properties in PbPb and pp collisions at $ \sqrt{s_{\mathrm{N}\;\mathrm{N}}}=5.02 $ TeV
Journal of High Energy Physics. 2018-05-02.
DOI : 10.1007/JHEP05(2018)006.
Modifications of the properties of jets in PbPb collisions, relative to those in pp collisions, are studied at a nucleon-nucleon center-of-mass energy of $ \sqrt{s_{\mathrm{N}\,\mathrm{N}}}=5.02 $ TeV via correlations of charged particles with the jet axis in relative pseudorapidity (Δη), relative azimuth (Δϕ), and relative angular distance from the jet axis $ \varDelta \mathrm{r}=\sqrt{{\left(\varDelta \eta \right)}^2+{\left(\varDelta \phi \right)}^2} $ . This analysis uses data collected with the CMS detector at the LHC, corresponding to integrated luminosities of 404 μb$^{−1}$ and 27.4 pb$^{−1}$ for PbPb and pp collisions, respectively. Charged particle number densities, jet fragmentation functions, and jet shapes are presented as a function of PbPb collision centrality and charged-particle track transverse momentum, providing a differential description of jet modifications due to interactions with the quark-gluon plasma.
Measurement of the $\Lambda_b$ polarization and angular parameters in $\Lambda_b\to J/\psi\, \Lambda$ decays from pp collisions at $\sqrt{s}=$ 7 and 8 TeV
Physical Review D. 2018-04-18.
DOI : 10.1103/PhysRevD.97.072010.
An analysis of the bottom baryon decay Λb→J/ψ(→μ+μ-)Λ(→pπ-) is performed to measure the Λb polarization and three angular parameters in data from pp collisions at s=7 and 8 TeV, collected by the CMS experiment at the Large Hadron Collider. The Λb polarization is measured to be 0.00±0.06(stat)±0.06(syst) and the parity-violating asymmetry parameter is determined to be 0.14±0.14(stat)±0.10(syst). The measurements are compared to various theoretical predictions, including those from perturbative quantum chromodynamics.
Search for lepton-flavor violating decays of heavy resonances and quantum black holes to eμ final states in proton-proton collisions at $ \sqrt{s}=13 $ TeV
Journal of High Energy Physics. 2018-04-13.
DOI : 10.1007/JHEP04(2018)073.
A search is reported for heavy resonances decaying into eμ final states in proton-proton collisions recorded by the CMS experiment at the CERN LHC at $ \sqrt{s}=13 $ TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The search focuses on resonance masses above 200 GeV. With no evidence found for physics beyond the standard model in the eμ mass spectrum, upper limits are set at 95% confidence level on the product of the cross section and branching fraction for this lepton-flavor violating signal. Based on these results, resonant τ sneutrino production in R-parity violating supersymmetric models is excluded for masses below 1.7 TeV, for couplings λ$_{132}$ = λ$_{231}$ = λ$_{311}^{′}$ = 0.01. Heavy Z$^{′}$ gauge bosons with lepton-flavor violating transitions are excluded for masses up to 4.4 TeV. The eμ mass spectrum is also interpreted in terms of non-resonant contributions from quantum black-hole production in models with one to six extra spatial dimensions, and lower mass limits are found between 3.6 and 5.6 TeV. In all interpretations used in this analysis, the results of this search improve previous limits by about 1 TeV. These limits correspond to the most sensitive values obtained at colliders.
Measurement of the associated production of a single top quark and a Z boson in pp collisions at $\sqrt{s} =$ 13 TeV
Physics Letters B. 2018-04-10.
DOI : 10.1016/j.physletb.2018.02.025.
A measurement is presented of the associated production of a single top quark and a Z boson. The study uses data from proton–proton collisions at s=13TeV recorded by the CMS experiment, corresponding to an integrated luminosity of 35.9 fb −1 . Using final states with three leptons (electrons or muons), the tZq production cross section is measured to be σ(pp→tZq→Wbℓ+ℓ−q)=123−31+33(stat)−23+29(syst)fb , where ℓ stands for electrons, muons, or τ leptons, with observed and expected significances of 3.7 and 3.1 standard deviations, respectively.
Combination of inclusive and differential $ \mathrm{t}\overline{\mathrm{t}} $ charge asymmetry measurements using ATLAS and CMS data at $ \sqrt{s}=7 $ and 8 TeV
Journal of High Energy Physics. 2018-04-09.
DOI : 10.1007/JHEP04(2018)033.
This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A$_{C}$) in top quark pair $ \left(\mathrm{t}\overline{\mathrm{t}}\right) $ events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb$^{−1}$ for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A$_{C}^{CHC7}$ = 0.005 ± 0.007 (stat) ± 0.006(syst) at 7 TeV and A$_{C}^{CHC8}$ = 0.0055 ± 0.0023 (stat) ± 0.0025 (syst) at 8 TeV. These values, as well as the combination of A$_{C}$ measurements as a function of the invariant mass of the $ \mathrm{t}\overline{\mathrm{t}} $ system at 8 TeV, are consistent with the respective standard model predictions.
Comparing transverse momentum balance of b jet pairs in pp and PbPb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV
Journal of High Energy Physics. 2018-03-29.
DOI : 10.1007/JHEP03(2018)181.
The transverse momentum balance of pairs of back-to-back b quark jets in PbPb and pp collisions recorded with the CMS detector at the LHC is reported. The center-of-mass energy in both collision systems is 5.02 TeV per nucleon pair. Compared to the pp collision baseline, b quark jets have a larger imbalance in the most central PbPb collisions, as expected from the jet quenching effect. The data are also compared to the corresponding measurement with inclusive dijets. In the most central collisions, the imbalance of b quark dijets is comparable to that of inclusive dijets.
Search for high-mass resonances in dilepton final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2018-03-16.
DOI : 10.1007/JHEP06(2018)120.
A search is presented for new high-mass resonances decaying into electron or muon pairs. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 36 fb$^{−1}$. Observations are in agreement with standard model expectations. Upper limits on the product of a new resonance production cross section and branching fraction to dileptons are calculated in a model-independent manner. This permits the interpretation of the limits in models predicting a narrow dielectron or dimuon resonance. A scan of different intrinsic width hypotheses is performed. Limits are set on the masses of various hypothetical particles. For the $ {Z}_{\mathrm{SSM}}^{\prime}\left({Z}_{{}^{\psi}}^{\prime}\right) $ particle, which arises in the sequential standard model (superstring-inspired model), a lower mass limit of 4.50 (3.90) TeV is set at 95% confidence level. The lightest Kaluza-Klein graviton arising in the Randall-Sundrum model of extra dimensions, with coupling parameters k/M$_{Pl}$ of 0.01, 0.05, and 0.10, is excluded at 95% confidence level below 2.10, 3.65, and 4.25 TeV, respectively. In a simplified model of dark matter production via a vector or axial vector mediator, limits at 95% confidence level are obtained on the masses of the dark matter particle and its mediator.
Evidence for associated production of a Higgs boson with a top quark pair in final states with electrons, muons, and hadronically decaying $\tau$ leptons at $\sqrt{s} =$ 13 TeV
Journal of High Energy Physics. 2018-03-14.
DOI : 10.1007/JHEP08(2018)066.
Results of a search for the standard model Higgs boson produced in association with a top quark pair ($\mathrm{t\overline{t}}$H) in final states with electrons, muons, and hadronically decaying $\tau$ leptons are presented. The analyzed data set corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS experiment in 2016. The sensitivity of the search is improved by using matrix element and machine learning methods to separate the signal from backgrounds. The measured signal rate amounts to 1.23 $^{+0.45}_{-0.43}$ times the production rate expected in the standard model, with an observed (expected) significance of 3.2$\sigma$ (2.8$\sigma$), which represents evidence for $\mathrm{t\overline{t}}$H production in those final states. An upper limit on the signal rate of 2.1 times the standard model production rate is set at 95% confidence level.
Search for third-generation scalar leptoquarks decaying to a top quark and a $\tau$ lepton at $\sqrt{s}=$ 13 TeV
The European Physical Journal C. 2018-03-07.
DOI : 10.1140/epjc/s10052-018-6143-z.
A search for pair production of heavy scalar leptoquarks (LQs), each decaying into a top quark and a $\tau$ lepton, is presented. The search considers final states with an electron or a muon, one or two $\tau$ leptons that decayed to hadrons, and additional jets. The data were collected in 2016 in proton-proton collisions at $\sqrt{s}=$ 13 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay LQ$ \to $t$\tau$, upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900 GeV at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a $\tau$ lepton.
Search for standard model production of four top quarks with same-sign and multilepton final states in proton–proton collisions at $\sqrt{s} = 13\,\text {TeV} $
The European Physical Journal C. 2018-02-19.
DOI : 10.1140/epjc/s10052-018-5607-5.
A search for standard model production of four top quarks ( $\mathrm {t}\overline{\mathrm {t}} \mathrm {t}\overline{\mathrm {t}} $ ) is reported using events containing at least three leptons ( $\mathrm {e}, \mathrm {\mu }$ ) or a same-sign lepton pair. The events are produced in proton–proton collisions at a center-of-mass energy of 13 $\,\text {TeV}$ at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ . Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the $\mathrm {t}\overline{\mathrm {t}} \mathrm {t}\overline{\mathrm {t}} $ cross section is measured to be $16.9^{+13.8-11.4}$ $\,\text {fb}$ , in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level.
Mapping Affinities in Academic Organizations
Frontiers in Research Metrics and Analytics. 2018-02-19.
DOI : 10.3389/frma.2018.00004.
Scholarly affinities are one of the most fundamental hidden dynamics that drive scientific development. Some affinities are actual, and consequently can be measured through classical academic metrics such as co-authoring. Other affinities are potential, and therefore do not leave visible traces in information systems; for instance, some peers may share interests without actually knowing it. This article illustrates the development of a map of affinities for academic collectives, designed to be relevant to three audiences: the management, the scholars themselves, and the external public. Our case study involves the School of Architecture, Civil and Environmental Engineering of EPFL, hereinafter ENAC. The school consists of around 1,000 scholars, 70 laboratories, and 3 institutes. The actual affinities are modeled using the data available from the information systems reporting publications, teaching, and advising scholars, whereas the potential affinities are addressed through text mining of the publications. The major challenge for designing such a map is to represent the multi-dimensionality and multi-scale nature of the information. The affinities are not limited to the computation of heterogeneous sources of information; they also apply at different scales. The map, thus, shows local affinities inside a given laboratory, as well as global affinities among laboratories. This article presents a graphical grammar to represent affinities. Its effectiveness is illustrated by two actualizations of the design proposal: an interactive online system in which the map can be parameterized, and a large-scale carpet of 250 square meters. In both cases, we discuss how the materiality influences the representation of data, in particular the way key questions could be appropriately addressed considering the three target audiences: the insights gained by the management and their consequences in terms of governance, the understanding of the scholars’ own positioning in the academic group in order to foster opportunities for new collaborations and, eventually, the interpretation of the structure from a general public to evaluate the relevance of the tool for external communication.
Negentropic linguistic evolution: A comparison of seven languages
2018. Digital Humanities 2018 , Mexico City, Mexico , June 26-29, 2018.
The relationship between the entropy of language and its complexity has been the subject of much speculation – some seeing the increase of linguistic entropy as a sign of linguistic complexification or interpreting entropy drop as a marker of greater regularity. Some evolutionary explanations, like the learning bottleneck hypothesis, argues that communication systems having more regular structures tend to have evolutionary advantages over more complex structures. Other structural effects of communication networks, like globalization of exchanges or algorithmic mediation, have been hypothesized to have a regularization effect on language. Longer-term studies are now possible thanks to the arrival of large-scale diachronic corpora, like newspaper archives or digitized libraries. However, simple analyses of such datasets are prone to misinterpretations due to significant variations of corpus size over the years and the indirect effect this can have on various measures of language change and linguistic complexity. In particular, it is important not to misinterpret the arrival of new words as an increase in complexity as this variation is intrinsical, as is the variation of corpus size. This paper is an attempt to conduct an unbiased diachronic study of linguistic complexity over seven different languages using the Google Books corpus. The paper uses a simple entropy measure on a closed, but nevertheless large, subset of words, called kernels. The kernel contains only the words that are present without interruption for the whole length of the study. This excludes all the words that arrived or disappeared during the period. We argue that this method is robust towards variations of corpus size and permits to study change in complexity despite possible (and in the case of Google Books unknown) change in the composition of the corpus. Indeed, the evolution observed on the seven different languages shows rather different patterns that are not directly correlated with the evolution of the size of the respective corpora. The rest of the paper presents the methods followed, the results obtained and the next steps we envision.
Deep Learning for Logic Optimization Algorithms
2018-01-01. IEEE International Symposium on Circuits and Systems (ISCAS) , Florence, ITALY , May 27-30, 2018.
The slowing down of Moore's law and the emergence of new technologies puts an increasing pressure on the field of EDA. There is a constant need to improve optimization algorithms. However, finding and implementing such algorithms is a difficult task, especially with the novel logic primitives and potentially unconventional requirements of emerging technologies. In this paper, we cast logic optimization as a deterministic Markov decision process (MDP). We then take advantage of recent advances in deep reinforcement learning to build a system that learns how to navigate this process. Our design has a number of desirable properties. It is autonomous because it learns automatically and does not require human intervention. It generalizes to large functions after training on small examples. Additionally, it intrinsically supports both single-and multioutput functions, without the need to handle special cases. Finally, it is generic because the same algorithm can be used to achieve different optimization objectives, e. g., size and depth.
Making large art historical photo archives searchable
Lausanne, EPFL, 2018.
DOI : 10.5075/epfl-thesis-8857.
In recent years, museums, archives and other cultural institutions have initiated important programs to digitize their collections. Millions of artefacts (paintings, engravings, drawings, ancient photographs) are now represented in digital photographic format. Furthermore, through progress in standardization, a growing portion of these images are now available online, in an easily accessible manner. This thesis studies how such large-scale art history collection can be made searchable using new deep learning approaches for processing and comparing images. It takes as a case study the processing of the photo archive of the Foundation Giorgio Cini, where more than 300'000 images have been digitized. We demonstrate how a generic processing pipeline can reliably extract the visual and textual content of scanned images, opening up ways to efficiently digitize large photo-collections. Then, by leveraging an annotated graph of visual connections, a metric is learnt that allows clustering and searching through artwork reproductions independently of their medium, effectively solving a difficult problem of cross-domain image search. Finally, the thesis studies how a complex Web Interface allows users to perform different searches based on this metric. We also evaluate the process by which users can annotate elements of interest during their navigation to be added to the database, allowing the system to be trained further and give better results. By documenting a complete approach on how to go from a physical photo-archive to a state-of-the-art navigation system, this thesis paves the way for a global search engine across the world's photo archives.
The Intellectual Organisation of History
Lausanne, EPFL, 2018.
DOI : 10.5075/epfl-thesis-8537.
A tradition of scholarship discusses the characteristics of different areas of knowledge, in particular after modern academia compartmentalized them into disciplines. The academic approach is often put to question: are there two or more cultures? Is an ever-increasing specialization the only way to cope with information abundance or are holistic approaches helpful too? What is happening with the digital turn? If these questions are well studied for the sciences, our understanding of how the humanities might differ in their own respect is far less advanced. In particular, modern academia might foster specific patterns of specialization in the humanities. Eventually, the recent rise in the application of digital methods to research, known as the digital humanities, might be introducing structural adaptations through the development of shared research technologies and the advent of organizational practices such as the laboratory. It therefore seems timely and urgent to map the intellectual organization of the humanities. This investigation depends on few traits such as the level of codification, the degree of agreement among scholars, the level of coordination of their efforts. These characteristics can be studied by measuring their influence on the outcomes of scientific communication. In particular, this thesis focuses on history as a discipline using bibliometric methods. In order to explore history in its complexity, an approach to create collaborative citation indexes in the humanities is proposed, resulting in a new dataset comprising monographs, journal articles and citations to primary sources. Historians' publications were found to organize thematically and chronologically, sharing a limited set of core sources across small communities. Core sources act in two ways with respect to the intellectual organization: locally, by adding connectivity within communities, or globally as weak ties across communities. Over recent decades, fragmentation is on the rise in the intellectual networks of historians, and a comparison across a variety of specialisms from the human, natural and mathematical sciences revealed the fragility of such networks across the axes of citation and textual similarities. Humanists organize into more, smaller and scattered topical communities than scientists. A characterisation of history is eventually proposed. Historians produce new historiographical knowledge with a focus on evidence or interpretation. The former aims at providing the community with an agreed-upon factual resource. Interpretive work is instead mainly focused on creating novel perspectives. A second axe refers to two modes of exploration of new ideas: in-breadth, where novelty relates to adding new, previously unknown pieces to the mosaic, or in-depth, if novelty then happens by improving on previous results. All combinations possible, historians tend to focus on in-breadth interpretations, with the immediate consequence that growth accentuates intellectual fragmentation in the absence of further consolidating factors such as theory or technologies. Research on evidence might have a different impact by potentially scaling-up in the digital space, and in so doing influence the modes of interpretation in turn. This process is not dissimilar to the gradual rise in importance of research technologies and collaborative competition in the mathematical and natural sciences. This is perhaps the promise of the digital humanities.
Mapping affinities: visualizing academic practice through collaboration
EPFL, 2018.
DOI : 10.5075/epfl-thesis-8242.
Academic affinities are one of the most fundamental hidden dynamics that drive scientific development. Some affinities are actual, and consequently can be measured through classical academic metrics such as co-authoring. Other affinities are potential, and therefore do not have visible traces in information systems; for instance, some peers may share scientific interests without actually knowing it. This thesis illustrates the development of a map of affinities for scientific collectives, which is intended to be relevant to three audiences: the management, the scholars themselves, and the external public. Our case study involves the School of Architecture, Civil and Environmental Engineering of EPFL, which consists of three institutes, seventy laboratories, and around one thousand employees. The actual affinities are modeled using the data available from the academic systems reporting publications, teaching, and advising, whereas the potential affinities are addressed through text mining of the documents registered in the information system. The major challenge for designing such a map is to represent the multi-dimensionality and multi-scale nature of the information. The affinities are not limited to the computation of heterogeneous sources of information, they also apply at different scales. Therefore, the map shows local affinities inside a given laboratory, as well as global affinities among laboratories. The thesis presents a graphical grammar to represent affinities. This graphical system is actualized in several embodiments, among which a large-scale carpet of 250 square meters and an interactive online system in which the map can be parameterized. In both cases, we discuss how the actualization influences the representation of data, in particular the way key questions could be appropriately addressed considering the three target audiences: the insights gained by the management and the relative decisions, the understanding of the researchersâ own positioning in the academic collective that might reveal opportunities for new synergies, and eventually the interpretation of the structure from an external standpoint that suggesting the relevance of the tool for communication.
2017
Search for the flavor-changing neutral current interactions of the top quark and the Higgs boson which decays into a pair of b quarks at $\sqrt{s}=$ 13 TeV
Journal of High Energy Physics. 2017-12-06.
DOI : 10.1007/JHEP06(2018)102.
A search for flavor-changing neutral currents (FCNC) in events with the top quark and the Higgs boson is presented. The Higgs boson decay to a pair of b quarks is considered. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ recorded by the CMS experiment at the LHC in proton-proton collisions at $ \sqrt{s}=13 $ TeV. Two channels are considered: single top quark FCNC production in association with the Higgs boson (pp → tH), and top quark pair production with FCNC decay of the top quark (t → qH). Final states with one isolated lepton and at least three reconstructed jets, among which at least two are associated with b quarks, are studied. No significant deviation is observed from the predicted background. Observed (expected) upper limits at 95% confidence level are set on the branching fractions of top quark decays, ℬ(t → uH) < 0.47% (0.34%) and ℬ(t → cH) < 0.47% (0.44%), assuming a single nonzero FCNC coupling.
Search for ZZ resonances in the 2$\ell$2$\nu$ final state in proton-proton collisions at 13 TeV
Journal of High Energy Physics. 2017-11-12.
DOI : 10.1007/JHEP03(2018)003.
A search for heavy resonances decaying to a pair of Z bosons is performed using data collected with the CMS detector at the LHC. Events are selected by requiring two oppositely charged leptons (electrons or muons), consistent with the decay of a Z boson, and large missing transverse momentum, which is interpreted as arising from the decay of a second Z boson to two neutrinos. The analysis uses data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The hypothesis of a spin-2 bulk graviton (X) decaying to a pair of Z bosons is examined for 600 ≤ m$_{X}$ ≤ 2500 GeV and upper limits at 95% confidence level are set on the product of the production cross section and branching fraction of X → ZZ ranging from 100 to 4 fb. For bulk graviton models characterized by a curvature scale parameter $ \tilde{k}=0.5 $ in the extra dimension, the region m$_{X}$ < 800 GeV is excluded, providing the most stringent limit reported to date. Variations of the model considering the possibility of a wide resonance produced exclusively via gluon-gluon fusion or $ \mathrm{q}\overline{\mathrm{q}} $ annihilation are also examined.
Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV
Journal of Instrumentation. 2017-02-22.
DOI : 10.1088/1748-0221/12/02/P02014.
Improved jet energy scale corrections, based on a data sample corresponding to an integrated luminosity of 19.7 fb(-1) collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 8 TeV, are presented. The corrections as a function of pseudorapidity η and transverse momentum p(T) are extracted from data and simulated events combining several channels and methods. They account successively for the effects of pileup, uniformity of the detector response, and residual data-simulation jet energy scale differences. Further corrections, depending on the jet flavor and distance parameter (jet size) R, are also presented. The jet energy resolution is measured in data and simulated events and is studied as a function of pileup, jet size, and jet flavor. Typical jet energy resolutions at the central rapidities are 15–20% at 30 GeV, about 10% at 100 GeV, and 5% at 1 TeV. The studies exploit events with dijet topology, as well as photon+jet, Z+jet and multijet events. Several new techniques are used to account for the various sources of jet energy scale corrections, and a full set of uncertainties, and their correlations, are provided.The final uncertainties on the jet energy scale are below 3% across the phase space considered by most analyses (p(T),>30 GeV and 0| η| <5.). In the barrel region (| η| <1.3) an uncertainty below 1% for p(T)>30 GeV is reached, when excluding the jet flavor uncertainties, which are provided separately for different jet flavors. A new benchmark for jet energy scale determination at hadron colliders is achieved with 0.32% uncertainty for jets with \pt of the order of 165–330\GeV, and | η| <0.8.
The CMS trigger system
Journal of Instrumentation. 2017-01-24.
DOI : 10.1088/1748-0221/12/01/P01020.
This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described.
Measurements of the $\mathrm{t}\overline{\mathrm{t}}$ production cross section in lepton+jets final states in pp collisions at 8 $\,\text {TeV}$ and ratio of 8 to 7 $\,\text {TeV}$ cross sections
The European Physical Journal C. 2017-01-07.
DOI : 10.1140/epjc/s10052-016-4504-z.
A measurement of the top quark pair production ( $\mathrm{t}\overline{\mathrm{t}} $ ) cross section in proton–proton collisions at the centre-of-mass energy of 8 $\,\text {TeV}$ is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6 $\,\text {fb}^{-\text {1}}$ . This analysis is performed in the $\mathrm{t}\overline{\mathrm{t}} $ decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured $\mathrm{t}\overline{\mathrm{t}} $ cross section is $228.5 \pm 3.8\,\text {(stat)} \pm 13.7\,\text {(syst)} \pm 6.0\,\text {(lumi)} \text { pb} $ . This measurement is compared with an analysis of 7 $\,\text {TeV}$ data, corresponding to an integrated luminosity of 5.0 $\,\text {fb}^{-\text {1}}$ , to determine the ratio of 8 $\,\text {TeV}$ to 7 $\,\text {TeV}$ cross sections, which is found to be $1.43 \pm 0.04\,\text {(stat)} \pm 0.07\,\text {(syst)} \pm 0.05\,\text {(lumi)} $ . The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
Layout Analysis on Newspaper Archives
2017. Digital Humanities 2017 , Montreal, Canada , August 8-11, 2017.
The study of newspaper layout evolution through historical corpora has been addressed by diverse qualitative and quantitative methods in the past few years. The recent availability of large corpora of newspapers is now making the quantitative analysis of layout evolution ever more popular. This research investigates a method for the automatic detection of layout evolution on scanned images with a factorial analysis approach. The notion of eigenpages is defined by analogy with eigenfaces used in face recognition processes. The corpus of scanned newspapers that was used contains 4 million press articles, covering about 200 years of archives. This method can automatically detect layout changes of a given newspaper over time, rebuilding a part of its past publishing strategy and retracing major changes in its history in terms of layout. Besides these advantages, it also makes it possible to compare several newspapers at the same time and therefore to compare the layout changes of multiple newspapers based only on scans of their issues.
Machine Vision Algorithms on Cadaster Plans
2017. Premiere Annual Conference of the International Alliance of Digital Humanities Organizations (DH 2017) , Montreal, Canada , August 8-11, 2017.
Cadaster plans are cornerstones for reconstructing dense representations of the history of the city. They provide information about the city urban shape, enabling to reconstruct footprints of most important urban components as well as information about the urban population and city functions. However, as some of these handwritten documents are more than 200 years old, the establishment of processing pipeline for interpreting them remains extremely challenging. We present the first implementation of a fully automated process capable of segmenting and interpreting Napoleonic Cadaster Maps of the Veneto Region dating from the beginning of the 19th century. Our system extracts the geometry of each of the drawn parcels, classifies, reads and interprets the handwritten labels.
Analyse multi-échelle de n-grammes sur 200 années d'archives de presse
Lausanne, EPFL, 2017.
DOI : 10.5075/epfl-thesis-8180.
The recent availability of large corpora of digitized texts over several centuries opens the way to new forms of studies on the evolution of languages. In this thesis, we study a corpus of 4 million press articles covering a period of 200 years. The thesis tries to measure the evolution of written French on this period at the level of words and expressions, but also in a more global way by attempting to define integrated measures of linguistic evolution. The methodological choice is to introduce a minimum of linguistic hypotheses in this study by developing new measures around the simple notion of n-gram, a sequence of n consecutive words. The thesis explores on this basis the potential of already known concepts as temporal frequency profiles and their diachronic correlations, but also introduces new abstractions such as the notion of resilient linguistic kernel or the decomposition of profiles into solidified expressions according to simple statistical models. Through the use of distributed computational techniques, it develops methods to test the relevance of these concepts on a large amount of textual data and thus allows to propose a virtual observatory of the diachronic evolutions associated with a given corpus. On this basis, the thesis explores more precisely the multi-scale dimension of linguistic phenomena by considering how standardized measures evolve when applied to increasingly long n-grams. The discrete and continuous scale from the isolated entities (n=1) to the increasingly complex and structured expressions (1 < n < 10) offers a transversal axis of study to the classical differentiations that ordinarily structure linguistics: syntax, semantics, pragmatics, and so on. The thesis explores the quantitative and qualitative diversity of phenomena at these different scales of language and develops a novel approach by proposing multi-scale measurements and formalizations, with the aim of characterizing more fundamental structural aspects of the studied phenomena.
Urban Development Processes: Methodological Investigation into the Complexity and Dynamics of Post-socialist Cities
Lausanne, EPFL, 2017.
DOI : 10.5075/epfl-thesis-7597.
The overall objective of this thesis is to critically address, break down and reassemble the urban development process in post-socialist cities through a set of analyses that covers urban planning strategies, real-estate interventions, participatory and urban design activities. The blurred and distorted morphology of cities worldwide requires dynamic solutions and calls for proper techniques that are spatially and temporally adjusted to local socio-spatial patterns. The theoretical foundations are built upon the ordinary cities approach. It provides a unique assemblage to examine how cities are intertwined with the world, without forgetting social, cultural and historical legacies inherent to each city. The urban development of post-socialist cities is thus perceived as a complex and dynamic system that incorporates discrepant layers of urban decision-making, tracks the level of urbanity through the fluctuating links between urban agency and socio-spatial patterns, and, in general, reveals the contextual processes of maintenance, transformation and change within an urban system. The case study of the Savamala neighbourhood, is not only a scaled example of the pre-socialist material legacy, a socialist cultural and regulatory matrix, and a transitional social reality, but equally the condensed illustration of the multi-faceted circumstances of post-socialist urban development. These elements constitute the exploratory boundaries for research pertaining to a decision-making chain, urban agency networks, and to socio-spatial patterns identified in Savamala through a qualitative data collection. The methodological framework is based on a process-driven, correlational research design that blends two methods. The Actor-Network Theory creates bottom-up logical argumentation to describe urban complexity. The Multi-Agent System serves to track urban dynamics and thus outline the action framework of the research. Data analysis, triangulation and reduction rely on complex actor roles and synthesized networks, the contextualization of interests and interventions, and the distribution of urban system transitions. The combination of overlapping methods and the visualization of data in diagrams deconstructs long-term historical processes. The research findings are three-folded. Firstly, they shed light on the actors and the processes at play in Savamala, unveiling a disbalanced conglomerate of sectors: political (power-mongers), economic (profit-seekers), professional (technicians and apparatchiks), civil and cultural (on the go). The articulation of urban agency in Savamala fundamentally confirms an authoritarian distribution of roles and decisions. The empirical results of the study contribute to the operationalization of several theoretical concepts for practical investigations in ordinary cities around the world. While urban development is interpreted in terms of contextualized urban system transitions, an overarching demarcation of the level of urbanity captures the fluctuations of local socio-spatial capital. The complexity of urban actors, forces, artefacts, and the dynamics of urban networks, interrelations, processes, are depicted as a legible, data-loaded scheme of nodes and links when data is visualised through the MAS-ANT methodological approach. This research furnishes a response to the necessity of altering a deterministic concept of urban research in terms of finding an intermediary between empirical data and their graphical display.
A Simple Set of Rules for Characters and Place Recognition in French Novels
Frontiers in Digital Humanities. 2017.
DOI : 10.3389/fdigh.2017.00006.
Big Data of the Past
Frontiers in Digital Humanities. 2017.
DOI : 10.3389/fdigh.2017.00012.
Big Data is not a new phenomenon. History is punctuated by regimes of data acceleration, characterized by feelings of information overload accompanied by periods of social transformation and the invention of new technologies. During these moments, private organizations, administrative powers, and sometimes isolated individuals have produced important datasets, organized following a logic that is often subsequently superseded but was at the time, nevertheless, coherent. To be translated into relevant sources of information about our past, these document series need to be redocumented using contemporary paradigms. The intellectual, methodological, and technological challenges linked to this translation process are the central subject of this article.
Narrative Recomposition in the Context of Digital Reading
Lausanne, EPFL, 2017.
DOI : 10.5075/epfl-thesis-7592.
In any creative process, the tools one uses have an immediate influence on the shape of the final artwork. However, while the digital revolution has redefined core values in most creative domains over the last few decades, its impact on literature remains limited. This thesis explores the relevance of digital tools for several aspects of novels writing by focusing on two research questions: Is it possible for an author to edit better novels out of already published ones, given the access to adapted tools? And, will authors change their way of writing when they know how they are being read? This thesis is a multidisciplinary participatory study, actively involving the Swiss novelist Daniel de Roulet, to construct measures, visualizations, and digital tools aimed at leveraging the process of dynamic reordering of narrative material, similar to how one edits a video footage. We developed and tested various text analysis and visualization tools, the results of which were interpreted and used by the author to recompose a family saga out of material he has been writing for twenty-four years. Based on this research, we released Saga+, an online editing, publishing, and reading tool. The platform was handed out to third parties to improve existing writings, making new novels available to the public as a result. While many researchers have studied the structuration of texts either through global statistical features or micro-syntactic analyses, we demonstrate that by allowing visualization and interaction at an intermediary level of organisation, authors can manipulate their own texts in agile ways. By integrating readersâ traces into this newly revealed structure, authors can start to approach the question of optimizing their writing processes in ways that are similar to what is being practiced in other media industries. The introduction of tools for optimal composition opens new avenues for authors, as well as a controversial debate regarding the future of literature.
Optimized scripting in Massive Open Online Courses
Dariah Teach, Université de Lausanne, Switzerland, March 23-24, 2017.
The Time Machine MOOC, currently under preparation, is designed to provide the necessary knowledge for students to use the editing tool of the Time Machine platform. The first test case of the platform in centered on our current work on the City of Venice and its archives. Small Teaching modules focus on specific skills of increasing difficulty: segmenting a word on a page, transcribing a word from a document series, georeferencing ancient maps using homologous points, disambiguating named entities, redrawing urban structures, finding matching details between paintings and writing scripts that perform automatically some of these tasks. Other skills include actions in the physical world, like scanning pages, books, maps or performing a photogrammetric reconstruction of a sculpture taking a large number of pictures. Eventually, some other modules are dedicated to general historic, linguistic, technical or archival knowledge that constitute prerequisites for mastering specific tasks. A general dependency graph has been designed, specifying in which order the skills can be acquired. The performance of most tasks can be tested using some pre-defined exercises and evaluation metrics, which allows for a precise evaluation of the level of mastery of each student. When the student successfully passes the test related to a skill, he or she gets the credentials to use that specific tool in the platform and starts contributing. However, the teaching options can vary greatly for each skill. Building upon the script concept developed by Dillenbourg and colleagues, we designed each tutorial as a parameterized sequence. A simple gradient descent method is used to progressively optimize the parameters in order to maximize the success rate of the students at the skill tests and therefore seek a form of optimality among the various design choices for the teaching methods. Thus, the more students use the platform, the more efficient teaching scripts become.
The references of references: a method to enrich humanities library catalogs with citation data
International Journal on Digital Libraries. 2017.
DOI : 10.1007/s00799-017-0210-1.
The advent of large-scale citation indexes has greatly impacted the retrieval of scientific information in several domains of research. The humanities have largely remained outside of this shift, despite their increasing reliance on digital means for information seeking. Given that publications in the humanities have a longer than average life-span, mainly due to the importance of monographs for the field, this article proposes to use domain-specific reference monographs to bootstrap the enrichment of library catalogs with citation data. Reference monographs are works considered to be of particular importance in a research library setting, and likely to possess characteristic citation patterns. The article shows how to select a corpus of reference monographs, and proposes a pipeline to extract the network of publications they refer to. Results using a set of reference monographs in the domain of the history of Venice show that only 7% of extracted citations are made to publications already within the initial seed. Furthermore, the resulting citation network suggests the presence of a core set of works in the domain, cited more frequently than average.
Studying Linguistic Changes over 200 Years of Newspapers through Resilient Words Analysis
Frontiers in Digital Humanities. 2017.
DOI : 10.3389/fdigh.2017.00002.
This paper presents a methodology to analyze linguistic changes in a given textual corpus allowing to overcome two common problems related to corpus linguistics studies. One of these issues is the monotonic increase of the corpus size with time, and the other one is the presence of noise in the textual data. In addition, our method allows to better target the linguistic evolution of the corpus, instead of other aspects like noise fluctuation or topics evolution. A corpus formed by two newspapers “La Gazette de Lausanne” and “Le Journal de Genève” is used, providing 4 million articles from 200 years of archives. We first perform some classical measurements on this corpus in order to provide indicators and visualizations of linguistic evolution. We then define the concept of a lexical kernel and word resilience, to face the two challenges of noises and corpus size fluctuations. This paper ends with a discussion based on the comparison of results from linguistic change analysis and concludes with possible future works continuing in that direction.
2016
Search for lepton flavour violating decays of the Higgs boson to $e \tau$ and $e \mu$ in proton–proton collisions at $\sqrt s=$ 8 TeV
Physics Letters B. 2016-12-10.
DOI : 10.1016/j.physletb.2016.09.062.
A direct search for lepton flavour violating decays of the Higgs boson (H) in the H→eτ and H→eμ channels is described. The data sample used in the search was collected in proton–proton collisions at s=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 fb −1 . No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H→eτ)<0.69% and B(H→eμ)<0.035% , are set at the 95% confidence level. The constraint set on B(H→eτ) is an order of magnitude more stringent than the existing indirect limits. The limits are used to constrain the corresponding flavour violating Yukawa couplings, absent in the standard model.
Search for R-parity violating decays of a top squark in proton-proton collisions at $\sqrt{s}$ = 8 TeV
Physics Letters B. 2016-09-10.
DOI : 10.1016/j.physletb.2016.06.039.
The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton–proton collisions at s=8 TeV , are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 fb −1 collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, t˜→tχ˜1±,χ˜1±→ℓ±+jj , top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling λijk′ (i,j,k≤2) , where i,j,k correspond to the three generations.
Measurement of the $ \mathrm{ Z } \gamma \rightarrow \nu \bar{\nu} \gamma$ production cross section in pp collisions at $\sqrt{s}=$ 8 TeV and limits on anomalous $ \mathrm{ ZZ } \gamma$ and $ \mathrm{Z} \gamma \gamma$ trilinear gauge boson couplings
Physics Letters B. 2016-09-10.
DOI : 10.1016/j.physletb.2016.06.080.
An inclusive measurement of the Zγ→νν‾γ production cross section in pp collisions at s=8TeV is presented, using data corresponding to an integrated luminosity of 19.6 fb −1 collected with the CMS detector at the LHC. This measurement is based on the observation of events with large missing energy and with a single photon with transverse momentum above 145 GeV and absolute pseudorapidity in the range |η|<1.44 . The measured Zγ→νν‾γ production cross section, 52.7±2.1 (stat)±6.4 (syst)±1.4 (lumi) fb , agrees well with the standard model prediction of 50.0−2.2+2.4 fb . A study of the photon transverse momentum spectrum yields the most stringent limits to date on the anomalous ZZγ and Zγγ trilinear gauge boson couplings.
Measurement of the differential cross sections for top quark pair production as a function of kinematic event variables in pp collisions at $\sqrt s$=7 and 8 TeV
Physical Review D. 2016-09-08.
DOI : 10.1103/PhysRevD.94.052006.
Measurements are reported of the normalized differential cross sections for top quark pair production with respect to four kinematic event variables: the missing transverse energy; the scalar sum of the jet transverse momentum (pT); the scalar sum of the pT of all objects in the event; and the pT of leptonically decaying W bosons from top quark decays. The data sample, collected using the CMS detector at the LHC, consists of 5.0 fb−1 of proton-proton collisions at s=7 TeV and 19.7 fb−1 at s=8 TeV. Top quark pair events containing one electron or muon are selected. The results are presented after correcting for detector effects to allow direct comparison with theoretical predictions. No significant deviations from the predictions of several standard model event simulation generators are observed.
Azimuthal decorrelation of jets widely separated in rapidity in pp collisions at $ \sqrt{s}=7 $ TeV
Journal of High Energy Physics. 2016-08-24.
DOI : 10.1007/JHEP08(2016)139.
The decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at the LHC at $ \sqrt{s}=7 $ TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Δϕ, between the Mueller-Navelet jets, the average cosines of (π − Δϕ), 2(π − Δϕ), and 3(π − Δϕ), and ratios of these cosines. The jets are required to have transverse momenta, p$_{T}$, in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Δy, between the Mueller-Navelet jets, reaching Δy up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes.
Search for direct pair production of supersymmetric top quarks decaying to all-hadronic final states in pp collisions at $\sqrt{s} = 8\;\text {TeV} $
The European Physical Journal C. 2016-08-16.
DOI : 10.1140/epjc/s10052-016-4292-5.
Results are reported from a search for the pair production of top squarks, the supersymmetric partners of top quarks, in final states with jets and missing transverse momentum. The data sample used in this search was collected by the CMS detector and corresponds to an integrated luminosity of 18.9 $\,\text {fb}^\text {-1}$ of proton-proton collisions at a centre-of-mass energy of 8 $\,\text {TeV}$ produced by the LHC. The search features novel background suppression and prediction methods, including a dedicated top quark pair reconstruction algorithm. The data are found to be in agreement with the predicted backgrounds. Exclusion limits are set in simplified supersymmetry models with the top squark decaying to jets and an undetected neutralino, either through a top quark or through a bottom quark and chargino. Models with the top squark decaying via a top quark are excluded for top squark masses up to 755 $\,\text {GeV}$ in the case of neutralino masses below 200 $\,\text {GeV}$ . For decays via a chargino, top squark masses up to 620 $\,\text {GeV}$ are excluded, depending on the masses of the chargino and neutralino.
Search for supersymmetry in events with soft leptons, low jet multiplicity, and missing transverse energy in proton–proton collisions at $\sqrt{s}$=8 TeV
Physics Letters B. 2016-08-10.
DOI : 10.1016/j.physletb.2016.05.033.
Results are presented from a search for supersymmetric particles in scenarios with small mass splittings. The data sample corresponds to 19.7 fb−1 of proton–proton collisions recorded by the CMS experiment at s=8 TeV . The search targets top squark ( t˜ ) pair production in scenarios with mass differences Δm=m(t˜)−m(χ˜10) below the W-boson mass and with top-squark decays in the four-body mode ( t˜→bℓνχ˜10 ), where the neutralino ( χ˜10 ) is assumed to be the lightest supersymmetric particle (LSP). The signature includes a high transverse momentum ( pT ) jet associated with initial-state radiation, one or two low- pT leptons, and significant missing transverse energy. The event yields observed in data are consistent with the expected background contributions from standard model processes. Limits are set on the cross section for top squark pair production as a function of the t˜ and LSP masses. Assuming a 100% branching fraction for the four-body decay mode, top-squark masses below 316 GeV are excluded for Δm=25 GeV at 95% CL. The dilepton data are also interpreted under the assumption of chargino–neutralino production, with subsequent decays to sleptons or sneutrinos. Assuming a difference between the common χ˜1+/χ˜20 mass and the LSP mass of 20 GeV and a τ -enriched decay scenario, masses in the range m(χ˜1+)<307 GeV are excluded at 95% CL.
Combined search for anomalous pseudoscalar HVV couplings in VH(H $\to b \bar b$) production and H $\to$ VV decay
Physics Letters B. 2016-08-10.
DOI : 10.1016/j.physletb.2016.06.004.
A search for anomalous pseudoscalar couplings of the Higgs boson H to electroweak vector bosons V ( =W or Z) in a sample of proton–proton collision events corresponding to an integrated luminosity of 18.9 fb −1 at a center-of-mass energy of 8 TeV is presented. Events consistent with the topology of associated VH production, where the Higgs boson decays to a pair of bottom quarks and the vector boson decays leptonically, are analyzed. The consistency of data with a potential pseudoscalar contribution to the HVV interaction, expressed by the effective pseudoscalar cross section fractions fa3 , is assessed by means of profile likelihood scans. Results are given for the VH channels alone and for a combined analysis of the VH and previously published H→VV channels. Under certain assumptions, fa3ZZ>0.0034 is excluded at 95% confidence level in the combination. Scenarios in which these assumptions are relaxed are also considered.
Search for neutral resonances decaying into a Z boson and a pair of b jets or $\tau$ leptons
Physics Letters B. 2016-08-10.
DOI : 10.1016/j.physletb.2016.05.087.
A search is performed for a new resonance decaying into a lighter resonance and a Z boson. Two channels are studied, targeting the decay of the lighter resonance into either a pair of oppositely charged τ leptons or a bb‾ pair. The Z boson is identified via its decays to electrons or muons. The search exploits data collected by the CMS experiment at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.8 fb −1 . No significant deviations are observed from the standard model expectation and limits are set on production cross sections and parameters of two-Higgs-doublet models.
Measurement of the inelastic cross section in proton–lead collisions at $\sqrt {s_{NN}}=$ 5.02 TeV
Physics Letters B. 2016-08-10.
DOI : 10.1016/j.physletb.2016.06.027.
The inelastic hadronic cross section in proton–lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of L=12.6±0.4 nb−1 , has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton–lead collisions with hadronic activity produced in the pseudorapidity ranges 3<η<5 and/or −5<η<−3 , corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be σinel(pPb)=2061±3(stat)±34(syst)±72(lumi) mb . Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of σinel(pPb) is compatible with that expected from the proton–proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.
Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at $ \sqrt{s}=7 $ and 8 TeV
Journal of High Energy Physics. 2016-08-05.
DOI : 10.1007/JHEP08(2016)045.
Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a W or a Z boson or a pair of top quarks, and of the six decay modes H → ZZ, W W , γγ, ττ, bb, and μμ. All results are reported assuming a value of 125.09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton-proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb$^{−1}$ at $ \sqrt{s}=7 $ TeV and 20 fb$^{−1}$ at $ \sqrt{s}=8 $ TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1.09 ± 0.11. The combined measurements lead to observed significances for the vector boson fusion production process and for the H → ττ decay of 5.4 and 5.5 standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered.
Measurement of the ${{\mathrm{W} }^{+} }\mathrm{W}^{-} $ cross section in pp collisions at $\sqrt{s} =$ 8 TeV and limits on anomalous gauge couplings
The European Physical Journal C. 2016-07-15.
DOI : 10.1140/epjc/s10052-016-4219-1.
A measurement of the W boson pair production cross section in proton-proton collisions at $\sqrt{s} = 8$ TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 19.4 $\,\text {fb}^\text {-1}$ . The ${{\mathrm{W} }^{+} }\mathrm{W}^{-} $ candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured ${{\mathrm{W} }^{+} }\mathrm{W}^{-} $ cross section is $60.1\pm 0.9\,\text {(stat)} \pm 3.2\,\text {(exp)} \pm 3.1\,\text {(theo)} \pm 1.6\,\text {(lumi)} \text {\,pb} = 60.1\pm 4.8\text {\,pb} $ , consistent with the standard model prediction. The ${{\mathrm{W} }^{+} }\mathrm{W}^{-} $ cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are $-5.7< c_{\mathrm {WWW}}/\Lambda ^2 < 5.9\,\mathrm{TeV}^{-2}$ , $-11.4< c_{\mathrm {W}}/\Lambda ^2 < 5.4\,\mathrm{TeV}^{-2}$ , $-29.2< c_{\mathrm {B}}/\Lambda ^2 < 23.9\,\mathrm{TeV}^{-2}$ , in the HISZ basis.
Search for a Low-Mass Pseudoscalar Higgs Boson Produced in Association with a $b\bar{b}$ Pair in $pp$ Collisions at $\sqrt{s} =$ 8 TeV
Physics Letters B. 2016-07-10.
DOI : 10.1016/j.physletb.2016.05.003.
A search is reported for a light pseudoscalar Higgs boson decaying to a pair of τ leptons, produced in association with a bb‾ pair, in the context of two-Higgs-doublet models. The results are based on pp collision data at a centre-of-mass energy of 8 TeV collected by the CMS experiment at the LHC and corresponding to an integrated luminosity of 19.7 fb −1 . Pseudoscalar boson masses between 25 and 80 GeV are probed. No evidence for a pseudoscalar boson is found and upper limits are set on the product of cross section and branching fraction to τ pairs between 7 and 39 pb at the 95% confidence level. This excludes pseudoscalar A bosons with masses between 25 and 80 GeV, with SM-like Higgs boson negative couplings to down-type fermions, produced in association with bb‾ pairs, in Type II, two-Higgs-doublet models.
Measurement of Spin Correlations in $t\bar{t}$ Production using the Matrix Element Method in the Muon+Jets Final State in $pp$ Collisions at $\sqrt{s} =$ 8 TeV
Physics Letters B. 2016-07-10.
DOI : 10.1016/j.physletb.2016.05.005.
The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon+jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb −1 . The data are compared with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72±0.08(stat)−0.13+0.15(syst) , representing the most precise measurement of this quantity in the muon+jets final state to date.
Measurement of $\mathrm {t}\overline{\mathrm {t}}$ production with additional jet activity, including $\mathrm {b}$ quark jets, in the dilepton decay channel using pp collisions at $\sqrt{s} =$ 8 TeV
The European Physical Journal C. 2016-07-07.
DOI : 10.1140/epjc/s10052-016-4105-x.
Jet multiplicity distributions in top quark pair ( ${{\rm t}}{\rm {\overline{t}}}$ ) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7 $\,\text {fb}^\text {-1}$ . The measurement is performed in the dilepton decay channels ( $\mathrm {e}^+\mathrm {e}^-$ , $\mathrm {\mu ^+}\mathrm {\mu ^-}$ , and $\mathrm {e}^{\pm }\mathrm {\mu }^{\mp }$ ). The absolute and normalized differential cross sections for $\mathrm {t}\overline{\mathrm {t}} $ production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential $\mathrm {\mathrm {t} \overline{\mathrm {t}} \mathrm {b}} $ and $\mathrm {\mathrm {t} \overline{\mathrm {t}} \mathrm {b} \overline{\mathrm {b}}} $ cross sections are presented for the first time as a function of the kinematic properties of the leading additional $\mathrm {b} $ jets. Furthermore, the fraction of events without additional jets above a threshold is measured as a function of the transverse momenta of the leading additional jets and the scalar sum of the transverse momenta of all additional jets. The data are compared and found to be consistent with predictions from several perturbative quantum chromodynamics event generators and a next-to-leading order calculation.
Search for the associated production of a Higgs boson with a single top quark in proton-proton collisions at $ \sqrt{s}=8 $ TeV
Journal of High Energy Physics. 2016-06-30.
DOI : 10.1007/JHEP06(2016)177.
This paper presents the search for the production of a Higgs boson in association with a single top quark (tHq), using data collected in proton-proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb$^{−1}$. The search exploits a variety of Higgs boson decay modes resulting in final states with photons, bottom quarks, and multiple charged leptons, including tau leptons, and employs a variety of multivariate techniques to maximize sensitivity to the signal. The analysis is optimized for the opposite sign of the Yukawa coupling to that in the standard model, corresponding to a large enhancement of the signal cross section. In the absence of an excess of candidate signal events over the background predictions, 95% confidence level observed (expected) upper limits on anomalous tHq production are set, ranging between 600 (450) fb and 1000 (700) fb depending on the assumed diphoton branching fraction of the Higgs boson. This is the first time that results on anomalous tHq production have been reported.
Search for pair-produced vectorlike B quarks in proton-proton collisions at $\sqrt{s}$=8 TeV
Physical Review D. 2016-06-15.
DOI : 10.1103/PhysRevD.93.112009.
A search for the production of a heavy B quark, having electric charge -1/3 and vector couplings to W, Z, and H bosons, is carried out using proton-proton collision data recorded at the CERN LHC by the CMS experiment, corresponding to an integrated luminosity of 19.7 fb−1. The B quark is assumed to be pair produced and to decay in one of three ways: to tW, bZ, or bH. The search is carried out in final states with one, two, and more than two charged leptons, as well as in fully hadronic final states. Each of the channels in the exclusive final-state topologies is designed to be sensitive to specific combinations of the B quark-antiquark pair decays. The observed event yields are found to be consistent with the standard model expectations in all the final states studied. A statistical combination of these results is performed, and upper limits are set on the cross section of the strongly produced B quark-antiquark pairs as a function of the B quark mass. Lower limits on the B quark mass between 740 and 900 GeV are set at a 95% confidence level, depending on the values of the branching fractions of the B quark to tW, bZ, and bH. Overall, these limits are the most stringent to date.
Forward–backward asymmetry of Drell–Yan lepton pairs in pp collisions at $\sqrt{s} = 8$ $\,\mathrm{TeV}$
The European Physical Journal C. 2016-06-14.
DOI : 10.1140/epjc/s10052-016-4156-z.
A measurement of the forward–backward asymmetry ${A}_{\mathrm{FB}}$ of oppositely charged lepton pairs ( $\mu \mu $ and $\mathrm{e}\mathrm{e}$ ) produced via $\mathrm{Z}/\gamma ^*$ boson exchange in pp collisions at $\sqrt{s} = 8$ $\,\mathrm{TeV}$ is presented. The data sample corresponds to an integrated luminosity of 19.7 $\,\mathrm{fb}^{-1}$ collected with the CMS detector at the LHC. The measurement of ${A}_{\mathrm{FB}}$ is performed for dilepton masses between 40 $\,\text {GeV}$ and 2 $\,\mathrm{TeV}$ and for dilepton rapidity up to 5. The ${A}_{\mathrm{FB}}$ measurements as a function of dilepton mass and rapidity are compared with the standard model predictions.
Inclusive and differential measurements of the $t\overline{t}$ charge asymmetry in pp collisions at $\sqrt{s} =$ 8 TeV
Physics Letters B. 2016-06-10.
DOI : 10.1016/j.physletb.2016.03.060.
The tt¯ charge asymmetry is measured in proton–proton collisions at a centre-of-mass energy of 8 TeV . The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 fb −1 . Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010±0.0068 (stat)±0.0037 (syst) . In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the tt¯ system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of −0.0035±0.0072 (stat)±0.0031 (syst) . All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model.
Measurement of the CP-violating weak phase $\phi_s$ and the decay width difference $\Delta \Gamma_s$ using the B$_s^0 \to J/\psi\phi$(1020) decay channel in pp collisions at $\sqrt{s}=$ 8 TeV
Physics Letters B. 2016-06-10.
DOI : 10.1016/j.physletb.2016.03.046.
The CP-violating weak phase ϕs of the Bs0 meson and the decay width difference ΔΓs of the Bs0 light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of Bs0→J/ψϕ(1020)→μ+μ−K+K− decays. The analysed data set corresponds to an integrated luminosity of 19.7fb−1 collected in pp collisions at a centre-of-mass energy of 8TeV . A total of 49 200 reconstructed Bs0 decays are used to extract the values of ϕs and ΔΓs by performing a time-dependent and flavour-tagged angular analysis of the μ+μ−K+K− final state. The weak phase is measured to be ϕs=−0.075±0.097(stat)±0.031(syst) rad , and the decay width difference is ΔΓs=0.095±0.013(stat)±0.007(syst) ps−1 .
Search for supersymmetry in events with a photon, a lepton, and missing transverse momentum in pp collisions at $\sqrt s=$ 8 TeV
Physics Letters B. 2016-06-10.
DOI : 10.1016/j.physletb.2016.03.039.
A search for supersymmetry involving events with at least one photon, one electron or muon, and large missing transverse momentum has been performed by the CMS experiment. The data sample corresponds to an integrated luminosity of 19.7 fb−1 of pp collisions at s=8 TeV , produced at the CERN LHC. No excess of events is observed beyond expectations from standard model processes. The result of the search is interpreted in the context of a general model of gauge-mediated supersymmetry breaking, where the charged and neutral winos are the next-to-lightest supersymmetric particles. Within this model, winos with a mass up to 360 GeV are excluded at the 95% confidence level. Two simplified models inspired by gauge-mediated supersymmetry breaking are also examined, and used to derive upper limits on the production cross sections of specific supersymmetric processes.
Measurement of the inclusive jet cross section in pp collisions at $\sqrt{s} = 2.76\,\text {TeV}$
The European Physical Journal C. 2016-05-12.
DOI : 10.1140/epjc/s10052-016-4083-z.
The double-differential inclusive jet cross section is measured as a function of jet transverse momentum $p_{\mathrm {T}}$ and absolute rapidity $|y |$ , using proton-proton collision data collected with the CMS experiment at the LHC, at a center-of-mass energy of $\sqrt{s} = 2.76\,{\mathrm{TeV}}$ and corresponding to an integrated luminosity of 5.43 $\,\text {pb}^{-1}$ . Jets are reconstructed within the $p_{\mathrm {T}}$ range of 74 to 592 $\,\text {GeV}$ and the rapidity range $|y |<3.0$ . The reconstructed jet spectrum is corrected for detector resolution. The measurements are compared to the theoretical prediction at next-to-leading-order QCD using different sets of parton distribution functions. This inclusive cross section measurement explores a new kinematic region and is consistent with QCD predictions.
Measurement of the ratio $B(B^0_s \to J/\psi f_0(980))$ / $B(B^0_s \to J/\psi \phi(1020))$ in pp collisions at $\sqrt s$ = 7 TeV
Physics Letters B. 2016-05-10.
DOI : 10.1016/j.physletb.2016.02.047.
A measurement of the ratio of the branching fractions of the Bs0 meson to J/ψf0(980) and to J/ψϕ(1020) is presented. The J/ψ , f0(980) , and ϕ(1020) are observed through their decays to μ+μ− , π+π− , and K+K− , respectively. The f0 and the ϕ are identified by requiring |Mπ+π−−974 MeV|<50 MeV and |MK+K−−1020 MeV|<10 MeV . The analysis is based on a data sample of pp collisions at a centre-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5.3 fb −1 . The measured ratio is B(Bs0→J/ψf0)B(f0→π+π−)B(Bs0→J/ψϕ)B(ϕ→K+K−)=0.140±0.008(stat)±0.023(syst) , where the first uncertainty is statistical and the second is systematic.
