[100] Search for light pseudoscalar boson pairs produced from decays of the 125 GeV Higgs boson in final states with two muons and two nearby tracks in pp collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search is presented for pairs of light pseudoscalar bosons, in the mass range from 4 to 15 GeV, produced from decays of the 125 GeV Higgs boson. The decay modes considered are final states that arise when one of the pseudoscalars decays to a pair of tau leptons, and the other one either into a pair of tau leptons or muons. The search is based on proton-proton collisions collected by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV that correspond to an integrated luminosity of 35.9 fb−1 . The 2μ2τ and 4 τ channels are used in combination to constrain the product of the Higgs boson production cross section and the branching fraction into 4 τ final state, σB , exploiting the linear dependence of the fermionic coupling strength of pseudoscalar bosons on the fermion mass. No significant excess is observed beyond the expectation from the standard model. The observed and expected upper limits at 95% confidence level on σB , relative to the standard model Higgs boson production cross section, are set respectively between 0.022 and 0.23 and between 0.027 and 0.19 in the mass range probed by the analysis.

DOI : 10.1016/j.physletb.2019.135087

[99] Real-Time Personalized Atrial Fibrillation Prediction on Multi-Core Wearable Sensors

E. De Giovanni; A. Arza Valdes; M. Peon Quiros; A. Aminifar; D. Atienza Alonso

In the recent Internet-of-Things (IoT) era where biomedical applications require continuous monitoring of relevant data, edge computing keeps gaining more and more importance. These new architectures for edge computing include multi-core and parallel computing capabilities that can enable prevention diagnosis and treatment of diseases in ambulatory or home-based setups. In this paper, we explore the benefits of the parallelization capabilities and computing heterogeneity of new wearable sensors in the context of a personalized online atrial fibrillation (AF) prediction method for daily monitoring. First, we apply optimizations to a single-core design to reduce energy, based on patient-specific training models. Second, we explore multi-core and memory banks configuration changes to adapt the computation and storage requirements to the characteristics of each patient. We evaluate our methodology on the Physionet Prediction Challenge (2001) publicly available database, and assess the energy consumption of single-core (ARM Cortex-M3 based) and new ultra-low power multi-core architectures (open-source RISC-V based) for next-generation of wearable platforms. Overall, our exploration at the application level highlights that a parallelization approach for personalized AF in multi-core wearable sensors enables energy savings up to 24% with respect to single-core sensors. Moreover, including the adaptation of the memory subsystem (size and number of memory banks), in combination with deep sleep energy saving modes, can overall provide total energy savings up to 34%, depending on the specific patient.

DOI : 10.1109/TETC.2020.3014847

[98] Modular Design and Optimization of Biomedical Applications for Ultra-Low Power Heterogeneous Platforms

E. De Giovanni; F. Montagna; B. W. Denkinger; S. Machetti; M. Peon Quiros  et al.

In the last years, remote health monitoring is becoming an essential branch of health care with the rapid development of wearable sensors technology. To meet the demand of new more complex applications and ensuring adequate battery lifetime, wearable sensors have evolved into multi-core systems with advanced power-saving capabilities and additional heterogeneous components. In this paper, we present an approach that applies optimization and parallelization techniques uncovered by modern ultra-low power platforms in the SW layers with the goal of improving the mapping and reducing the energy consumption of biomedical applications. Additionally, we investigate the benefit of integrating domain-specific accelerators to further reduce the energy consumption of the most computationally expensive kernels. Using 30-second excerpts of signals from two public databases, we apply the proposed optimization techniques on well-known modules of biomedical benchmarks from the state-of-the-art and two complete applications. We observe speed-ups of 5.17x and energy savings of 41.6% for the multi-core implementation using a cluster of 8 cores with respect to single-core wearable sensor designs when processing a standard 12-lead ECG signal analysis. Additionally, we conclude that the minimum workload required to take advantage of parallelization for a hearbeat classifier corresponds to the processing of 3-lead ECG signals, with a speed-up of 2.96x and energy savings of 19.3%. Moreover, we observe additional energy savings of up to 7.75% and 16.8% by applying power management and memory scaling to the multi-core implementation of the 3-lead beat classifier and 12-lead ECG analysis, respectively. Finally, by integrating hardware (HW) acceleration we observe overall energy savings of up to 51.3% for the 12-lead ECG analysis.

DOI : 10.1109/TCAD.2020.3012652

[97] Search for a narrow resonance lighter than 200 GeV decaying to a pair of muons in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is presented for a narrow resonance decaying to a pair of oppositely charged muons using $\sqrt{s}=$ 13 TeV proton-proton collision data recorded at the LHC. In the 45-75 and 110-200 GeV resonance mass ranges, the search is based on conventional triggering and event reconstruction techniques. In the 11.5-45 GeV mass range, the search uses data collected with dimuon triggers with low transverse momentum thresholds, recorded at high rate by storing a reduced amount of trigger-level information. The data correspond to integrated luminosities of 137 fb$^{-1}$ and 96.6 fb$^{-1}$ for conventional and high-rate triggering, respectively. No significant resonant peaks are observed in the probed mass ranges. The search sets the most stringent constraints to date on a dark photon in the $\sim$30-75 and 110-200 GeV mass ranges.

[96] Search for long-lived particles using delayed photons in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for long-lived particles decaying to photons and weakly interacting particles, using proton-proton collision data at s=13  TeV collected by the CMS experiment in 2016–2017 is presented. The data set corresponds to an integrated luminosity of 77.4  fb-1. Results are interpreted in the context of supersymmetry with gauge-mediated supersymmetry breaking, where the neutralino is long-lived and decays to a photon and a gravitino. Limits are presented as a function of the neutralino proper decay length and mass. For neutralino proper decay lengths of 0.1, 1, 10, and 100 m, masses up to 320, 525, 360, and 215 GeV are excluded at 95% confidence level, respectively. We extend the previous best limits in the neutralino proper decay length by up to one order of magnitude, and in the neutralino mass by up to 100 GeV.

DOI : 10.1103/PhysRevD.100.112003

[95] Determination of the strong coupling constant $\alpha_{S}(m_\mathrm{Z})$ from measurements of inclusive W$^\pm$ and Z boson production cross sections in proton-proton collisions at $\sqrt{s} =$ 7 and 8 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Twelve measurements of inclusive cross sections of W$^\pm$ and Z boson production, performed in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, are compared with perturbative quantum chromodynamics calculations at next-to-next-to-leading order (NNLO) accuracy obtained with the CT14, HERAPDF2.0, MMHT14, and NNPDF3.0 parton distribution functions (PDFs). Data and theory agree well for all PDF sets, taking into account the experimental and theoretical uncertainties. A novel procedure is employed to extract the strong coupling constant at the Z pole mass from a detailed comparison of all the experimental fiducial cross sections to the corresponding NNLO theoretical predictions, yielding $\alpha_{S}(m_\mathrm{Z}) =$ 0.1163$^{+0.0024}_{-0.0031}$ (CT14), 0.1072$^{+0.0043}_{-0.0040}$ (HERAPDF2.0), 0.1186$\pm$0.0025 (MMHT14), and 0.1147$\pm$0.0023 (NNPDF3.0). Using the results obtained with the CT14 and MMHT14 PDFs, which yield the most robust and stable $\alpha_{S}(m_\mathrm{Z})$ extractions, a value $\alpha_{S}(m_\mathrm{Z}) =$ 0.1175$^{+0.0025}_{-0.0028}$ is determined.

[94] Performance of the reconstruction and identification of high-momentum muons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The CMS detector at the LHC has recorded events from proton-proton collisions, with muon momenta reaching up to 1.8 TeV in the collected dimuon samples. These high-momentum muons allow direct access to new regimes in physics beyond the standard model. Because the physics and reconstruction of these muons are different from those of their lower-momentum counterparts, this paper presents for the first time dedicated studies of efficiencies, momentum assignment, resolution, scale, and showering of very high momentum muons produced at the LHC. These studies are performed using the 2016 and 2017 data sets of proton-proton collisions at $\sqrt{s} =$ 13 TeV with integrated luminosities of 36.3 and 42.1 fb$^{-1}$, respectively.

[93] Constraints on anomalous HVV couplings from the production of Higgs bosons decaying to $\tau$ lepton pairs

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A study is presented of anomalous HVV interactions of the Higgs boson, including its CP properties. The study uses Higgs boson candidates produced mainly in vector boson fusion and gluon fusion that subsequently decay to a pair of τ leptons. The data were recorded by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 35.9  fb-1. A matrix element technique is employed for the analysis of anomalous interactions. The results are combined with those from the H→4ℓ decay channel presented earlier, yielding the most stringent constraints on anomalous Higgs boson couplings to electroweak vector bosons expressed as effective cross section fractions and phases: the CP-violating parameter fa3cos(ϕa3)=(0.00±0.27)×10-3 and the CP-conserving parameters fa2cos(ϕa2)=(0.08-0.21+1.04)×10-3, fΛ1cos(ϕΛ1)=(0.00-0.09+0.53)×10-3, and fΛ1Zγcos(ϕΛ1Zγ)=(0.0-1.3+1.1)×10-3. The current dataset does not allow for precise constraints on CP properties in the gluon fusion process. The results are consistent with standard model expectations.

DOI : 10.1103/PhysRevD.100.112002

[92] Search for low-mass quark-antiquark resonances produced in association with a photon at $\sqrt{s} = $ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for narrow low-mass resonances decaying to quark-antiquark pairs is presented. The search is based on proton-proton collision events collected at 13 TeV by the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 35.9  fb-1, recorded in 2016. The search considers the case where the resonance has high transverse momentum due to initial-state radiation of a hard photon. To study this process, the decay products of the resonance are reconstructed as a single large-radius jet with two-pronged substructure. The signal would be identified as a localized excess in the jet invariant mass spectrum. No evidence for such a resonance is observed in the mass range 10 to 125 GeV. Upper limits at the 95% confidence level are set on the coupling strength of resonances decaying to quark pairs. The results obtained with this photon trigger strategy provide the first direct constraints on quark-antiquark resonance masses below 50 GeV obtained at a hadron collider.

DOI : 10.1103/PhysRevLett.123.231803

[91] Isospin amplitudes in $\Lambda_b^0\to J/\psi \Lambda(\Sigma^0)$ and $\Xi_b^0\to J/\psi \Xi^0(\Lambda)$ decays

R. Aaij; C. Abellán Beteta; T. Ackernley; B. Adeva; M. Adinolfi  et al.

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions, and allow searches for physics beyond the Standard Model. We present the first results on isospin amplitudes in $b$-baryon decays, using data corresponding to an integrated luminosity of 8.5 fb$^{-1}$, collected with the LHCb detector in $pp$ collisions at center of mass energies of 7, 8 and 13 TeV. The isospin amplitude ratio $|A_1(\Lambda_b^0\to J/\psi \Sigma^0)/A_0(\Lambda_b^0\to J/\psi\Lambda)|$, where the subscript on $A$ indicates the final-state isospin, is measured to be less than $1/20.9$ at 95\% confidence level. The Cabibbo suppressed $\Xi_b^0\to J/\psi\Lambda$ decay is observed for the first time, allowing for the measurement $|A_0(\Xi_b^0\to J/\psi\Lambda)/A_{1/2}(\Xi_b^0\to J/\psi\Xi^0)| =0.44 \pm 0.06\pm 0.02$, where the uncertainties are statistical and systematic, respectively.

[90] Search for a heavy Higgs boson decaying to a pair of W bosons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for a heavy Higgs boson in the mass range from 0.2 to 3.0 TeV, decaying to a pair of W bosons, is presented. The analysis is based on proton-proton collisions at $\sqrt{s} =$ 13 TeV recorded by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The W boson pair decays are reconstructed in the 2$\ell$2$\nu$ and $\ell\nu$2q final states (with $\ell =$ e or $\mu$). Both gluon fusion and vector boson fusion production of the signal are considered. Interference effects between the signal and background are also taken into account. The observed data are consistent with the standard model (SM) expectation. Combined upper limits at 95% confidence level on the product of the cross section and branching fraction exclude a heavy Higgs boson with SM-like couplings and decays up to 1870 GeV. Exclusion limits are also set in the context of a number of two-Higgs-doublet model formulations, further reducing the allowed parameter space for SM extensions.

[89] A search for the standard model Higgs boson decaying to charm quarks

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb$^{-1}$, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W$\to \ell \nu$, Z$\to \ell\ell$, and Z$\to \nu\nu$, where $\ell$ is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section $\sigma$(H)$\mathcal{B}$(H $\to \mathrm{c\bar{c}}$) of 4.5 (2.4$^{+1.0}_{-0.7}$) pb, corresponding to 70 (37) times the standard model prediction.

[88] Measurement of the top quark pair production cross section in dilepton final states containing one $\tau$ lepton in pp collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The cross section of top quark pair production is measured in the $\mathrm{t\bar{t}}\to (\ell\nu_{\ell})(\tau_\mathrm{h}\nu_{\tau})\mathrm{b\bar{b}}$ final state, where $\tau_\mathrm{h}$ refers to the hadronic decays of the $\tau$ lepton, and $\ell$ is either an electron or a muon. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ collected in proton-proton collisions at $\sqrt{s}=$ 13 TeV with the CMS detector. The measured cross section is $\sigma_{\mathrm{t\bar{t}}} =$ 781 $\pm$ 7 (stat) $\pm$ 62 (syst) $\pm$ 20 (lum) pb, and the ratio of the partial width $\Gamma($t$\to\tau\nu_{\tau}$b) to the total decay width of the top quark is measured to be 0.1050 $\pm$ 0.0009 (stat) $\pm$ 0.0071 (syst). This is the first measurement of the $\mathrm{t\bar{t}}$ production cross section in proton-proton collisions at $\sqrt{s}=$ 13 TeV that explicitly includes $\tau$ leptons. The ratio of the cross sections in the $\ell\tau_\mathrm{h}$ and $\ell\ell$ final states yields a value $R_{\ell\tau_\mathrm{h}/\ell\ell}=$ 0.973 $\pm$ 0.009 (stat) $\pm$ 0.066 (syst), consistent with lepton universality.

[87] Measurements of triple-differential cross sections for inclusive isolated-photon+jet events in pp collisions at $\sqrt{s} =$ 8 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Measurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in pp collisions at $\sqrt{s} =$ 8 TeV as a function of photon transverse momentum ($p_\mathrm{T}^\gamma$), photon pseudorapidity ($\eta^\gamma$), and jet pseudorapidity ($\eta^\text{jet}$). The data correspond to an integrated luminosity of 19.7 fb$^{-1}$ that probe a broad range of the available phase space, for $|\eta^\gamma|$ $<$ 1.44 and 1.57 $<$ $|\eta^\gamma|$ $<$ 2.50, $|\eta^\text{jet}|$ $<$ 2.5, 40 $<$ $p_\mathrm{T}^\gamma$ $<$ 1000 GeV, and jet transverse momentum, $p_\mathrm{T}^\text{jet}$, $>$ 25 GeV. The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.

DOI : 10.1140/epjc/s10052-019-7451-7

[86] Search for lepton flavour violating decays of a neutral heavy Higgs boson to $\mu\tau$ and e$\tau$ in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for lepton flavour violating decays of a neutral non-standard-model Higgs boson in the $\mu\tau$ and e$\tau$ decay modes is presented. The search is based on proton-proton collisions at a center of mass energy $\sqrt{s}=$ 13 TeV collected with the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The $\tau$ leptons are reconstructed in the leptonic and hadronic decay modes. No signal is observed in the mass range 200-900 GeV. At 95% confidence level, the observed (expected) upper limits on the production cross section multiplied by the branching fraction vary from 51.9 (57.4) fb to 1.6 (2.1) fb for the $\mu\tau$ and from 94.1 (91.6) fb to 2.3 (2.3) fb for the e$\tau$ decay modes.

[85] Precision measurement of the $\Xi_{cc}^{++}$ mass

R. Aaij; C. Abellán Beteta; T. Ackernley; B. Adeva; M. Adinolfi  et al.

A measurement of the $\Xi_{cc}^{++}$ mass is performed using data collected by the LHCb experiment between 2016 and 2018 in $pp$ collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.6 $\mathrm{fb}^{-1}$. The $\Xi_{cc}^{++}$ candidates are reconstructed via the decay modes $\Xi_{cc}^{++}\to\Lambda_c^+K^-\pi^+\pi^+$ and $\Xi_{cc}^{++}\to\Xi_c^+\pi^+$. The result, $3621.55 \pm 0.23{\rm\,(stat)\,} \pm 0.30 {\rm\,(syst)\,}{\rm MeV}/c^2$, is the most precise measurement of the $\Xi_{cc}^{++}$ mass to date.

[84] Search for supersymmetry in pp collisions at $\sqrt{s}=$ 13 TeV with 137 fb$^{-1}$ in final states with a single lepton using the sum of masses of large-radius jets

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Results are reported from a search for new physics beyond the standard model in proton-proton collisions in final states with a single lepton; multiple jets, including at least one jet tagged as originating from the hadronization of a bottom quark; and large missing transverse momentum. The search uses a sample of proton-proton collision data at $\sqrt{s}=$ 13 TeV, corresponding to 137 fb$^{-1}$, recorded by the CMS experiment at the LHC. The signal region is divided into categories characterized by the total number of jets, the number of bottom quark jets, the missing transverse momentum, and the sum of masses of large-radius jets. The observed event yields in the signal regions are consistent with estimates of standard model backgrounds based on event yields in the control regions. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production in which each gluino decays into a top quark-antiquark pair and a stable, unobserved neutralino, which generates missing transverse momentum in the event. Scenarios with gluino masses up to about 2150 GeV are excluded at 95% confidence level (or more) for neutralino masses up to 700 GeV. The highest excluded neutralino mass is about 1250 GeV, which holds for gluino masses around 1850 GeV.

[83] Search for the production of four top quarks in the single-lepton and opposite-sign dilepton final states in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for the standard model production of four top quarks (pp → $ \mathrm{t}\overline{\mathrm{t}}\mathrm{t}\overline{\mathrm{t}} $) is reported using single-lepton plus jets and opposite-sign dilepton plus jets signatures. Proton-proton collisions are recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV in a sample corresponding to an integrated luminosity of 35.8 fb$^{−}^{1}$. A multivariate analysis exploiting global event and jet properties is used to discriminate $ \mathrm{t}\overline{\mathrm{t}}\mathrm{t}\overline{\mathrm{t}} $ from $ \mathrm{t}\overline{\mathrm{t}} $ production. No significant deviation is observed from the predicted background. An upper limit is set on the cross section for $ \mathrm{t}\overline{\mathrm{t}}\mathrm{t}\overline{\mathrm{t}} $ production in the standard model of 48 fb at 95% confidence level. When combined with a previous measurement by the CMS experiment from an analysis of other final states, the observed signal significance is 1.4 standard deviations, and the combined cross section measurement is $ {13}_{-9}^{+11} $ fb. The result is also interpreted in the framework of effective field theory.

DOI : 10.1007/JHEP11(2019)082

[82] Search for physics beyond the standard model in multilepton final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for physics beyond the standard model in events with at least three charged leptons (electrons or muons) is presented. The data sample corresponds to an integrated luminosity of 137 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 13 TeV, collected with the CMS detector at the LHC in 2016-2018. The two targeted signal processes are pair production of type-III seesaw heavy fermions and production of a light scalar or pseudoscalar boson in association with a pair of top quarks. The heavy fermions may be manifested as an excess of events with large values of leptonic transverse momenta or missing transverse momentum. The light scalars or pseudoscalars may create a localized excess in the dilepton mass spectra. The results exclude heavy fermions of the type-III seesaw model for masses below 880 GeV at 95% confidence level in the scenario of equal branching fractions to each lepton flavor. This is the most restrictive limit on the flavor-democratic scenario of the type-III seesaw model to date. Assuming a Yukawa coupling of unit strength to top quarks, branching fractions of new scalar (pseudoscalar) bosons to dielectrons or dimuons above 0.004 (0.03) and 0.04 (0.03) are excluded at 95% confidence level for masses in the range 15-75 and 108-340 GeV, respectively. These are the first limits in these channels on an extension of the standard model with scalar or pseudoscalar particles.

[81] Search for anomalous electroweak production of vector boson pairs in association with two jets in proton-proton collisions at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets in proton-proton collisions at s=13TeV at the LHC is reported. The data sample corresponds to an integrated luminosity of 35.9fb−1 collected with the CMS detector. Events are selected by requiring two jets with large rapidity separation and invariant mass, one or two leptons (electrons or muons), and a W or Z boson decaying hadronically. No excess of events with respect to the standard model background predictions is observed and constraints on the structure of quartic vector boson interactions in the framework of dimension-8 effective field theory operators are reported. Stringent limits on parameters of the effective field theory operators are obtained. The observed 95% confidence level limits for the S0, M0, and T0 operators are −2.7<fS0/Λ4<2.7 , −1.0<fM0/Λ4<1.0 , and −0.17<fT0/Λ4<0.16 , in units of TeV −4 . Constraints are also reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass from 600 to 2000 GeV. The results are interpreted in the context of the Georgi–Machacek model.

DOI : 10.1016/j.physletb.2019.134985

[80] Combination of CMS searches for heavy resonances decaying to pairs of bosons or leptons

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb −1 collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with expectations from the standard model background. Exclusion limits are set in the context of models of spin-1 heavy vector triplets and of spin-2 bulk gravitons. For mass-degenerate W′ and Z′ resonances that predominantly couple to the standard model gauge bosons, the mass exclusion at 95% confidence level of heavy vector bosons is extended to 4.5 TeV as compared to 3.8 TeV determined from the best individual channel. This excluded mass increases to 5.0 TeV if the resonances couple predominantly to fermions.

DOI : 10.1016/j.physletb.2019.134952

[79] Search for MSSM Higgs bosons decaying to $\mu^+\mu^-$ in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is performed for neutral non-standard-model Higgs bosons decaying to two muons in the context of the minimal supersymmetric standard model (MSSM). Proton-proton collision data recorded by the CMS experiment at the CERN Large Hadron Collider at a center-of-mass energy of 13 TeV were used, corresponding to an integrated luminosity of 35.9 fb−1 . The search is sensitive to neutral Higgs bosons produced via the gluon fusion process or in association with a bb‾ quark pair. No significant deviations from the standard model expectation are observed. Upper limits at 95% confidence level are set in the context of the mhmod+ and phenomenological MSSM scenarios on the parameter tan⁡β as a function of the mass of the pseudoscalar A boson, in the range from 130 to 600 GeV. The results are also used to set a model-independent limit on the product of the branching fraction for the decay into a muon pair and the cross section for the production of a scalar neutral boson, either via gluon fusion, or in association with b quarks, in the mass range from 130 to 1000 GeV.

DOI : 10.1016/j.physletb.2019.134992

[78] Search for high mass dijet resonances with a new background prediction method in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for narrow and broad resonances with masses greater than 1.8 TeV decaying to a pair of jets is presented. The search uses proton-proton collision data at $\sqrt{s}=$13 TeV collected at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$. The background arising from standard model processes is predicted with the fit method used in previous publications and with a new method. The dijet invariant mass spectrum is well described by both data-driven methods, and no significant evidence for the production of new particles is observed. Model independent upper limits are reported on the production cross sections of narrow resonances, and broad resonances with widths up to 55% of the resonance mass. Limits are presented on the masses of narrow resonances from various models: string resonances, scalar diquarks, axigluons, colorons, excited quarks, color-octet scalars, W' and Z' bosons, Randall-Sundrum gravitons, and dark matter mediators. The limits on narrow resonances are improved by 200 to 800 GeV relative to those reported in previous CMS dijet resonance searches. The limits on dark matter mediators are presented as a function of the resonance mass and width, and on the associated coupling strength as a function of the mediator mass. These limits exclude at 95% confidence level a dark matter mediator with a mass of 1.8 TeV and width 1% of its mass or higher, up to one with a mass of 4.8 TeV and a width 45% of its mass or higher.

[77] Measurement of the jet mass distribution and top quark mass in hadronic decays of boosted top quarks in pp collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A measurement is reported of the jet mass distribution in hadronic decays of boosted top quarks produced in pp collisions at $\sqrt{s}=$ 13 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The measurement is performed in the lepton+jets channel of $\mathrm{t\bar{t}}$ events, where the lepton is an electron or muon. The products of the hadronic top quark decay t$\to$bW$\to$bq$\mathrm{\bar{q}}'$ are reconstructed as a single jet with transverse momentum larger than 400 GeV. The $\mathrm{t\bar{t}}$ cross section as a function of the jet mass is unfolded at the particle level and used to extract a value of the top quark mass of 172.6 $\pm$ 2.5 GeV. A novel jet reconstruction technique is used for the first time at the LHC, which improves the precision by a factor of three relative to an earlier measurement.

[76] Observation of the $\Lambda_\mathrm{b}^0 \to$ J/$\psi \Lambda \phi$ decay in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The observation of the $\Lambda_\mathrm{b}^0 \to$J/$\psi \Lambda \phi$ decay is reported using proton-proton collision data collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio of the branching fractions $\mathcal{B}(\Lambda_\mathrm{b}^0 \to$J/$\psi \Lambda \phi)/\mathcal{B}(\Lambda_\mathrm{b}^0\to\psi \Lambda)$ is measured to be (8.26$\pm$0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 $(\mathcal{B}))\times $10$^{-2}$, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of $\phi$ and $\psi$(2S) decays to the reconstructed final states.

[75] Search for new neutral Higgs bosons through the H$\to$ ZA $\to \ell^{+}\ell^{-} \mathrm{b\bar{b}}$ process in pp collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

This paper reports on a search for an extended scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy $\sqrt{s} = $ 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Data and predictions from the standard model are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model.

[74] Search for dijet resonances using events with three jets in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for a narrow resonance with a mass between 350 and 700 GeV, and decaying into a pair of jets, is performed using proton-proton collision events containing at least three jets. The data sample corresponds to an integrated luminosity of 18.3 fb$^{-1}$ recorded at $\sqrt{s}=$ 13 TeV with the CMS detector. Data are collected with a technique known as "data scouting", in which the events are reconstructed, selected, and recorded at a high rate in a compact form by the high-level trigger. The three-jet final state provides sensitivity to lower resonance masses than in previous searches using the data scouting technique. The spectrum of the dijet invariant mass, calculated from the two jets with the largest transverse momenta in the event, is used to search for a resonance. No significant excess over a smoothly falling background is found. Limits at 95% confidence level are set on the production cross section of a narrow dijet resonance. The corresponding upper limits on the coupling of a narrow vector resonance interacting only with quarks are between 0.10 and 0.15, depending on the resonance mass. These results represent the most stringent upper limits in the mass range between 350 and 450 GeV obtained with a search that is sensitive to the decay of the resonance into light-flavor quarks.

[73] Measurement of the average very forward energy as a function of the track multiplicity at central pseudorapidities in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The average total energy as well as its hadronic and electromagnetic components are measured with the CMS detector at pseudorapidities $-6.6<\eta <-5.2$ in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=13\,\text {TeV} $ . The results are presented as a function of the charged particle multiplicity in the region $|\eta |<2$ . This measurement is sensitive to correlations induced by the underlying event structure over a very wide pseudorapidity region. The predictions of Monte Carlo event generators commonly used in collider experiments and ultra-high energy cosmic ray physics are compared to the data. All generators considered overestimate the fraction of energy going into hadrons.

DOI : 10.1140/epjc/s10052-019-7402-3

[72] Studies of charm quark diffusion inside jets using PbPb and pp collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with $p_\mathrm{T}^\mathrm{jet}>$ 60 GeV and D$^0$ mesons with $p_\mathrm{T}^\mathrm{D}>$ 4 GeV in lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV, recorded by the CMS detector at the LHC. The radial distribution of D$^0$ mesons with respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in PbPb collisions. When compared to Monte Carlo event generators, the radial distribution in pp collisions is found to be well-described by PYTHIA, while the slope of the distribution predicted by SHERPA is steeper than that of the data. In PbPb collisions, compared to the pp results, the D$^0$ meson distribution for $4 < p_\mathrm{T}^\mathrm{D}<$ 20 GeV hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. At higher $p_\mathrm{T}^\mathrm{D}$, the PbPb and pp radial distributions are found to be similar.

[71] Search for new physics in top quark production in dilepton final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for new physics in top quark production is performed in proton-proton collisions at $13\,\text {TeV} $ . The data set corresponds to an integrated luminosity of $35.9{\,\text {fb}^{-1}} $ collected in 2016 with the CMS detector. Events with two opposite-sign isolated leptons (electrons or muons), and $\mathrm{b}$ quark jets in the final state are selected. The search is sensitive to new physics in top quark pair production and in single top quark production in association with a $\mathrm{W}$ boson. No significant deviation from the standard model expectation is observed. Results are interpreted in the framework of effective field theory and constraints on the relevant effective couplings are set, one at a time, using a dedicated multivariate analysis. This analysis differs from previous searches for new physics in the top quark sector by explicitly separating $\mathrm{t}\mathrm{W}$ from $\mathrm{t}{\bar{\mathrm{t}}}$  events and exploiting the specific sensitivity of the $\mathrm{t}\mathrm{W}$ process to new physics.

DOI : 10.1140/epjc/s10052-019-7387-y

[70] Search for top squark pair production in a final state with two tau leptons in proton-proton collisions at $ \sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for pair production of the supersymmetric partner of the top quark, the top squark, in proton-proton collision events at $ \sqrt{s} =$ 13 TeV is presented in a final state containing hadronically decaying tau leptons and large missing transverse momentum. This final state is highly sensitive to high-$\tan{\beta}$ or higgsino-like scenarios in which decays of electroweak gauginos to tau leptons are dominant. The search uses a data set corresponding to an integrated luminosity of 77.2 fb$^{-1}$, which was recorded with the CMS detector during 2016 and 2017. No significant excess is observed with respect to the background prediction. Exclusion limits at 95% confidence level are presented in the top squark and lightest neutralino mass plane within the framework of simplified models, in which top squark masses up to 1100 GeV are excluded for a nearly massless neutralino.

[69] Measurement of properties of B$^0_\mathrm{s}\to\mu^+\mu^-$ decays and search for B$^0\to\mu^+\mu^-$ with the CMS experiment

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Results are reported for the B$^0_\mathrm{s}\to\mu^+\mu^-$ branching fraction and effective lifetime and from a search for the decay B$^0\to\mu^+\mu^-$. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7 TeV (5 fb$^{-1}$), 8 TeV (20 fb$^{-1}$), and 13 TeV (36 fb$^{-1}$). The branching fractions are determined by measuring event yields relative to B$^+\to$J/$\psi$K$^+$ decays (with J/$\psi\to\mu^+\mu^-$), which results in the reduction of many of the systematic uncertainties. The decay B$^0_\mathrm{s}\to\mu^+\mu^-$ is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be $\mathcal{B}$(B$^0_\mathrm{s}\to\mu^+\mu^-$) = [2.9$ ^{+0.7}_{-0.6}$ (exp)$\pm$0.2(frag)]$\times 10^{-9}$, where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the B$^0_\mathrm{s}$ and the B$^+$ fragmentation functions. No significant excess is observed for the decay B$^0\to\mu^+\mu^-$, and an upper limit of $\mathcal{B}$(B$^0\to\mu^+\mu^-$) < 3.6$\times$10$^{-10}$ is obtained at 95% confidence level. The B$^0_\mathrm{s}\to\mu^+\mu^-$ effective lifetime is measured to be $\tau_{\mu^+\mu^-}$= 1.70$^{+0.61}_{-0.44}$ ps. These results are consistent with standard model predictions.

[68] Search for supersymmetry in proton-proton collisions at 13 TeV in final states with jets and missing transverse momentum

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Results are reported from a search for supersymmetric particles in the final state with multiple jets and large missing transverse momentum. The search uses a sample of proton-proton collisions at $ \sqrt{s} $ = 13 TeV collected with the CMS detector in 2016–2018, corresponding to an integrated luminosity of 137 fb$^{−1}$, representing essentially the full LHC Run 2 data sample. The analysis is performed in a four-dimensional search region defined in terms of the number of jets, the number of tagged bottom quark jets, the scalar sum of jet transverse momenta, and the magnitude of the vector sum of jet transverse momenta. No significant excess in the event yield is observed relative to the expected background contributions from standard model processes. Limits on the pair production of gluinos and squarks are obtained in the framework of simplified models for supersymmetric particle production and decay processes. Assuming the lightest supersymmetric particle to be a neutralino, lower limits on the gluino mass as large as 2000 to 2310 GeV are obtained at 95% confidence level, while lower limits on the squark mass as large as 1190 to 1630 GeV are obtained, depending on the production scenario.

DOI : 10.1007/JHEP10(2019)244

[67] Search for a heavy pseudoscalar Higgs boson decaying into a 125 GeV Higgs boson and a Z boson in final states with two tau and two light leptons at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is performed for a pseudoscalar Higgs boson, A, decaying into a 125 GeV Higgs boson h and a Z boson. The h boson is specifically targeted in its decay into a pair of tau leptons, while the Z boson decays into a pair of electrons or muons. A data sample of proton-proton collisions collected by the CMS experiment at the LHC at $\sqrt{s} =$ 13 TeV is used, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No excess above the standard model background expectations is observed in data. A model-independent upper limit is set on the product of the gluon fusion production cross section for the A boson and the branching fraction to Zh$\to\ell\ell\tau\tau$. The observed upper limit at 95% confidence level ranges from 27 to 5 fb for A boson masses from 220 to 400 GeV, respectively. The results are used to constrain the extended Higgs sector parameters for two benchmark scenarios of the minimal supersymmetric standard model.

[66] Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at $\sqrt{s_\mathrm{NN}} =$ 5.44 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 5.44 TeV are presented. The measurements are based on data collected by the CMS experiment at the LHC. The yield of primary charged hadrons produced in xenon-xenon collisions in the pseudorapidity range $|\eta|$ $<$ 3.2 is determined using the silicon pixel detector in the CMS tracking system. For the 5% most central collisions, the charged-hadron pseudorapidity density in the midrapidity region $|\eta|$ $<$ 0.5 is found to be 1187 $\pm$ 36 (syst), with a negligible statistical uncertainty. The rapidity distribution of charged hadrons is also presented in the range $|y|$ $<$ 3.2 and is found to be independent of rapidity around $y =$ 0. Existing Monte-Carlo event generators are unable to simultaneously describe both results. Comparisons of charged-hadron multiplicities between xenon-xenon and lead-lead collisions at similar collision energies show that particle production at midrapidity is strongly dependent on the collision geometry in addition to the system size and collision energy.

DOI : 10.1016/j.physletb.2019.135049

[65] Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 2.76 and 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Anisotropies in the initial energy density distribution of the quark-gluon plasma created in high energy heavy ion collisions lead to anisotropies in the azimuthal distributions of the final-state particles known as collective flow. Fourier harmonic decomposition is used to quantify these anisotropies. The higher-order harmonics can be induced by the same order anisotropies (linear response) or by the combined influence of several lower order anisotropies (nonlinear response) in the initial state. The mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles are measured as functions of transverse momentum and centrality in PbPb collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_\mathrm{NN}} =$ 2.76 and 5.02 TeV with the CMS detector. The results are compared with viscous hydrodynamic calculations using several different initial conditions, as well as microscopic transport model calculations. None of the models provides a simultaneous description of the mixed higher-order flow harmonics and nonlinear response coefficients.

[64] Bose-Einstein correlations of charged hadrons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Bose-Einstein correlations of charged hadrons are measured over a broad multiplicity range, from a few particles up to about 250 reconstructed charged hadrons in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The results are based on data collected using the CMS detector at the LHC during runs with a special low-pileup configuration. Three analysis techniques with different degrees of dependence on simulations are used to remove the non-Bose-Einstein background from the correlation functions. All three methods give consistent results. The measured lengths of homogeneity are studied as functions of particle multiplicity as well as average pair transverse momentum and mass. The results are compared with data from both CMS and ATLAS at $\sqrt{s} =$ 7 TeV, as well as with theoretical predictions.

[63] Measurement of the top quark Yukawa coupling from $\mathrm{t\bar{t}}$ kinematic distributions in the lepton+jets final state in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Results are presented for an extraction of the top quark Yukawa coupling from top quark-antiquark (tt¯) kinematic distributions in the lepton plus jets final state in proton-proton collisions, based on data collected by the CMS experiment at the LHC at s=13  TeV, corresponding to an integrated luminosity of 35.8  fb-1. Corrections from weak boson exchange, including Higgs bosons, between the top quarks can produce large distortions of differential distributions near the energy threshold of tt¯ production. Therefore, precise measurements of these distributions are sensitive to the Yukawa coupling. Top quark events are reconstructed with at least three jets in the final state, and a novel technique is introduced to reconstruct the tt¯ system for events with one missing jet. This technique enhances the experimental sensitivity in the low invariant mass region, Mtt¯. The data yields in Mtt¯, the rapidity difference |yt-yt¯|, and the number of reconstructed jets are compared with distributions representing different Yukawa couplings. These comparisons are used to measure the ratio of the top quark Yukawa coupling to its standard model predicted value to be 1.07-0.43+0.34 with an upper limit of 1.67 at the 95% confidence level.

DOI : 10.1103/PhysRevD.100.072007

[62] Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Evidence for the light-by-light scattering process, γγ→γγ , in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390μb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy ETγ>2GeV , pseudorapidity |ηγ|<2.4 , diphoton invariant mass mγγ>5GeV , diphoton transverse momentum pTγγ<1GeV , and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0±0.9(theo) events for the signal and 4.0±1.2(stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ→γγ)=120±46(stat)±28(syst)±12(theo)nb , is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the Image 1 process, in the mass range Image 2 .

DOI : 10.1016/j.physletb.2019.134826

[61] Search for Higgs and Z boson decays to J/ψ or Y pairs in the four-muon final state in proton-proton collisions at s=13TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for decays of the Higgs and Z boson to pairs of J/ψ or Y(nS) (n = 1, 2, 3) mesons, with their subsequent decay to μ+μ− pairs, is presented. The analysis uses data from proton-proton collisions at s=13TeV , collected with the CMS detector at the LHC in 2017 and corresponding to an integrated luminosity of 37.5 fb−1 . While an observation of such a decay with this sample would indicate the presence of physics beyond the standard model, no significant excess is observed. Upper limits at 95% confidence level are placed on the branching fractions of these decays. In the J/ψ pair channel, the limits are 1.8×10−3 and 2.2×10−6 for the Higgs and Z boson, respectively, while in the combined Y(nS) pair channel, the limits are 1.4×10−3 and 1.5×10−6 , respectively, when the mesons from the Higgs and Z boson decay are assumed to be unpolarized. When fully longitudinal and transverse polarizations are considered the limits reduce by about 22–29% and increase by about 10–13%, respectively.

DOI : 10.1016/j.physletb.2019.134811

[60] Search for long-lived particles using nonprompt jets and missing transverse momentum with proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for long-lived particles decaying to displaced, nonprompt jets and missing transverse momentum is presented. The data sample corresponds to an integrated luminosity of 137 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2016–2018. Candidate signal events containing nonprompt jets are identified using the timing capabilities of the CMS electromagnetic calorimeter. The results of the search are consistent with the background prediction and are interpreted using a gauge-mediated supersymmetry breaking reference model with a gluino next-to-lightest supersymmetric particle. In this model, gluino masses up to 2100, 2500, and 1900 GeV are excluded at 95% confidence level for proper decay lengths of 0.3, 1, and 100 m, respectively. These are the best limits to date for such massive gluinos with proper decay lengths greater than ∼0.5 m.

DOI : 10.1016/j.physletb.2019.134876

[59] Search for dark photons in decays of Higgs bosons produced in association with Z bosons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is presented for a Higgs boson that is produced in association with a Z boson and that decays to an undetected particle together with an isolated photon. The search is performed by the CMS Collaboration at the Large Hadron Collider using a data set corresponding to an integrated luminosity of 137 fb$^{−}^{1}$ recorded at a center-of-mass energy of 13 TeV. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for associated Higgs and Z boson production and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a mass of 125 GeV, assuming the standard model production cross section, this corresponds to an observed (expected) upper limit on this branching fraction of 4.6 (3.6)% at 95% confidence level. These are the first limits on Higgs boson decays to final states that include an undetected massless dark photon.

DOI : 10.1007/JHEP10(2019)139

[58] Strange hadron production in pp and pPb collisions at $\sqrt{s_\mathrm{NN}}= $ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The transverse momentum ($p_\mathrm{T}$) distributions of $\Lambda$, $\Xi^-$, and $\Omega^-$ baryons, their antiparticles, and K$^0_\mathrm{S}$ mesons are measured in proton-proton (pp) and proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV over a broad rapidity range. The data, corresponding to integrated luminosities of 40.2 nb$^{-1}$ and 15.6 $\mu$b$^{-1}$ for pp and pPb collisions, respectively, were collected by the CMS experiment. The nuclear modification factor $R_\mathrm{pPb}$, defined as the ratio of the particle yield in pPb collisions and a scaled pp reference, is measured for each particle. A strong dependence on particle species is observed in the $p_\mathrm{T}$ range from 2 to 7 GeV, where $R_\mathrm{pPb}$ for K$^0_\mathrm{S}$ is consistent with unity, while an enhancement ordered by strangeness content and/or particle mass is observed for the three baryons. In pPb collisions, the strange hadron production is asymmetric about the nucleon-nucleon center-of-mass rapidity. Enhancements, which depend on the particle type, are observed in the direction of the Pb beam. The results are compared to predictions from EPOS LHC, which includes parametrized radial flow. The model is in qualitative agreement with the $R_\mathrm{pPb}$ data, but fails to describe the dependence on particle species in the yield asymmetries measured away from mid-rapidity in pPb collisions.

[57] Search for resonances decaying to a pair of Higgs bosons in the $\mathrm{b\overline{b}q\overline{q}'}\ell\nu$ final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for new massive particles decaying into a pair of Higgs bosons in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. Data were collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{−}^{1}$. The search is performed for resonances with a mass between 0.8 and 3.5 TeV using events in which one Higgs boson decays into a bottom quark pair and the other decays into two W bosons that subsequently decay into a lepton, a neutrino, and a quark pair. The Higgs boson decays are reconstructed with techniques that identify final state quarks as substructure within boosted jets. The data are consistent with standard model expectations. Exclusion limits are placed on the product of the cross section and branching fraction for generic spin-0 and spin-2 massive resonances. The results are interpreted in the context of radion and bulk graviton production in models with a warped extra spatial dimension. These are the best results to date from searches for an HH resonance decaying to this final state, and they are comparable to the results from searches in other channels for resonances with masses below 1.5 TeV.

DOI : 10.1007/JHEP10(2019)125

[56] Search for pair production of vectorlike quarks in the fully hadronic final state

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The results of two searches for pair production of vectorlike T or B quarks in fully hadronic final states are presented, using data from the CMS experiment at a center-of-mass energy of 13 TeV. The data were collected at the LHC during 2016 and correspond to an integrated luminosity of 35.9  fb-1. A cut-based analysis specifically targets the bW decay mode of the T quark and allows for the reconstruction of the T quark candidates. In a second analysis, a multiclassification algorithm, the “boosted event shape tagger,” is deployed to label candidate jets as originating from top quarks, and W, Z, and H. Candidate events are categorized according to the multiplicities of identified jets, and the scalar sum of all observed jet momenta is used to discriminate signal events from the quantum chromodynamics multijet background. Both analyses probe all possible branching fraction combinations of the T and B quarks and set limits at 95% confidence level on their masses, ranging from 740 to 1370 GeV. These results represent a significant improvement relative to existing searches in the fully hadronic final state.

DOI : 10.1103/PhysRevD.100.072001

[55] Measurement of the top quark polarization and $\mathrm{t\bar{t}}$ spin correlations using dilepton final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Measurements of the top quark polarization and top quark pair (tt¯) spin correlations are presented using events containing two oppositely charged leptons (e+e-, e±μ∓, or μ+μ-) produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9  fb-1. A set of parton-level normalized differential cross sections, sensitive to each of the independent coefficients of the spin-dependent parts of the tt¯ production density matrix, is measured for the first time at 13 TeV. The measured distributions and extracted coefficients are compared with standard model predictions from simulations at next-to-leading-order (NLO) accuracy in quantum chromodynamics (QCD), and from NLO QCD calculations including electroweak corrections. All measurements are found to be consistent with the expectations of the standard model. The normalized differential cross sections are used in fits to constrain the anomalous chromomagnetic and chromoelectric dipole moments of the top quark to -0.24<CtG/Λ2<0.07  TeV-2 and -0.33<CtGI/Λ2<0.20  TeV-2, respectively, at the 95% confidence level.

DOI : 10.1103/PhysRevD.100.072002

[54] REWARD: Design, Optimization, and Evaluation of a Real-Time Relative-Energy Wearable R-Peak Detection Algorithm *

L. Orlandic; E. De Giovanni; A. Arza; S. Yazdani; J.-M. Vesin  et al.

Wearable devices are an unobtrusive, cost-effective means of continuous ambulatory monitoring of chronic cardiovascular diseases. However, on these resource-constrained systems, electrocardiogram (ECG) processing algorithms must consume minimal power and memory, yet robustly provide accurate physiological information. This work presents REWARD, the Relative-Energy-based WeArable R-Peak Detection algorithm, which is a novel ECG R-peak detection mechanism based on a nonlinear filtering method called Relative-Energy (Rel-En). REWARD is designed and optimized for real-time execution on wearable systems. Then, this novel algorithm is compared against three state-of-the-art real-time R-peak detection algorithms in terms of accuracy, memory footprint, and energy consumption. The Physionet QT and NST Databases were employed to evaluate the algorithms' accuracy and robustness to noise, respectively. Then, a 32-bit ARM Cortex-M3-based microcontroller was used to measure the energy usage, computational burden, and memory footprint of the four algorithms. REWARD consumed at least 63% less energy and 32% less RAM than the other algorithms while obtaining comparable accuracy results. Therefore, REWARD would be a suitable choice of R-peak detection mechanism for wearable devices that perform more complex ECG analysis, whose algorithms require additional energy and memory resources.

[53] Charged-particle angular correlations in XeXe collisions at $\sqrt{s_{_\mathrm{NN}}}=$ 5.44 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of sNN=5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42μb−1. The collective motion of the system formed in the collision is parametrized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients v2, v3, and v4 are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods. Within a hydrodynamic picture, these methods have different sensitivities to noncollective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenon-xenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.

DOI : 10.1103/PhysRevC.100.044902

[52] Study of J/$\psi$ meson production from jet fragmentation in pp collisions at $\sqrt{s} =$ 8 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A study of the production of prompt J/$\psi$ mesons as fragmentation products of jets in proton-proton collisions at $\sqrt{s} =$ 8 TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb$^{-1}$ collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/$\psi$ meson and the jet is used to test whether the J/$\psi$ meson is a jet fragment. The analysis shows that most prompt J/$\psi$ mesons with energy above 15 GeV and rapidity $|y|<$ 1 are fragments of jets with pseudorapidity $|\eta_{\text{jet}}| <$ 1. The differential distributions of the jet fragmentation probability as a function of jet energy for a fixed J/$\psi$ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/$\psi$ mesons are unpolarized. This technique demonstrates a new way to test predictions for prompt J/$\psi$ production using nonrelativistic quantum chromodynamics.

[51] Search for supersymmetry with a compressed mass spectrum in events with a soft $\tau$ lepton, a highly energetic jet, and large missing transverse momentum in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The first search for supersymmetry in events with an experimental signature of one soft, hadronically decaying $\tau$ lepton, one energetic jet from initial-state radiation, and large transverse momentum imbalance is presented. These event signatures are consistent with direct or indirect production of scalar $\tau$ leptons ($\tilde{\tau}$) in supersymmetric models that exhibit coannihilation between the $\tilde{\tau}$ and the lightest neutralino ($\tilde{\chi}^0_1$), and that could generate the observed relic density of dark matter. The data correspond to an integrated luminosity of 77.2 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}=$ 13 TeV collected with the CMS detector at the LHC in 2016 and 2017. The results are interpreted in a supersymmetric scenario with a small mass difference ($\Delta m$) between the chargino ($\tilde{\chi}^\pm_1$) or next-to-lightest neutralino ($\tilde{\chi}^0_2$), and the $\tilde{\chi}^0_1$. The mass of the $\tilde{\tau}$ is assumed to be the average of the $\tilde{\chi}^\pm_1$ and $\tilde{\chi}^0_1$ masses. The data are consistent with standard model background predictions. Upper limits at 95% confidence level are set on the sum of the $\tilde{\chi}^\pm_1$, $\tilde{\chi}^0_2$, and $\tilde{\tau}$ production cross sections for $\Delta m(\tilde{\chi}^\pm_1, \tilde{\chi}^0_1) =$ 50 GeV, resulting in a lower limit of 290 GeV on the mass of the $\tilde{\chi}^\pm_1$, which is the most stringent to date and surpasses the bounds from the LEP experiments.

[50] Calibration of the CMS hadron calorimeters using proton-proton collision data at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Methods are presented for calibrating the hadron calorimeter system of the CMS detector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities $|\eta| <$ 3 and are positioned inside a solenoidal magnet. An outer calorimeter, outside the magnet coil, covers $|\eta|<$ 1.26, and a steel and quartz-fiber Cherenkov forward calorimeter extends the coverage to $|\eta| <$ 5.2. The initial calibration of the calorimeters was based on results from test beams, augmented with the use of radioactive sources and lasers. The calibration was improved substantially using proton-proton collision data collected at $\sqrt{s} =$ 7, 8, and 13 TeV, as well as cosmic ray muon data collected during the periods when the LHC beams were not present. The present calibration is performed using the early 13 TeV data collected during 2016 corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The intercalibration of channels exploits the approximate uniformity of energy deposit over the azimuthal angle. The absolute energy scale of the central and endcap calorimeters is set using isolated charged hadrons. The energy scale for the electromagnetic portion of the forward calorimeters is set using Z $\to$ ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy.

[49] Search for a light charged Higgs boson decaying to a W boson and a CP-odd Higgs boson in final states with e$\mu\mu$ or $\mu\mu\mu$ in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for a light charged Higgs boson (H+) decaying to a W boson and a CP-odd Higgs boson (A) in final states with eμμ or μμμ is performed using data from pp collisions at s=13  TeV, recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9  fb-1. In this search, it is assumed that the H+ boson is produced in decays of top quarks, and the A boson decays to two oppositely charged muons. The presence of signals for H+ boson masses between 100 and 160 GeV and A boson masses between 15 and 75 GeV is investigated. No evidence for the production of the H+ boson is found. Upper limits at 95% confidence level are obtained on the combined branching fraction for the decay chain, t→bH+→bW+A→bW+μ+μ-, of 1.9×10-6 to 8.6×10-6, depending on the masses of the H+ and A bosons. These are the first limits for these decay modes of the H+ and A bosons.

DOI : 10.1103/PhysRevLett.123.131802

[48] Running of the top quark mass from proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The running of the top quark mass is experimentally investigated for the first time. The mass of the top quark in the modified minimal subtraction ($\mathrm{\overline{MS}}$) renormalization scheme is extracted from a comparison of the differential top quark-antiquark ($\mathrm{t\overline{t}}$) cross section as a function of the invariant mass of the $\mathrm{t\overline{t}}$ system to next-to-leading-order theoretical predictions. The differential cross section is determined at the parton level by means of a maximum-likelihood fit to distributions of final-state observables. The analysis is performed using $\mathrm{t\overline{t}}$ candidate events in the e$^\pm\mu^\mp$ channel in proton-proton collision data at a centre-of-mass energy of 13 TeV recorded by the CMS detector at the CERN LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The extracted running is found to be compatible with the scale dependence predicted by the corresponding renormalization group equation. In this analysis, the running is probed up to a scale of the order of 1 TeV.

[47] Azimuthal separation in nearly back-to-back jet topologies in inclusive 2- and 3-jet events in pp collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, $\varDelta \phi _{12}$ , is presented. The measurement considers events where the two leading jets are nearly collinear (“back-to-back”) in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of $13\,\text {Te}\text {V} $ and corresponding to an integrated luminosity of $35.9{\,\text {fb}^{-1}} $ are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region $177^\circ< \varDelta \phi _{12} < 180^\circ $ . The 2- and 3-jet measurements are not simultaneously described by any of models.

DOI : 10.1140/epjc/s10052-019-7276-4

[46] Evidence for WW production from double-parton interactions in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for WW production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a center-of-mass energy of 13 TeV. The analyzed data set corresponds to an integrated luminosity of 77.4 fb$^{-1}$, collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for WW production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is 1.41 $\pm$ 0.28 (stat) $\pm$ 0.28 (syst) pb.

[45] Measurement of the $\mathrm{t\bar{t}}\mathrm{b\bar{b}}$ production cross section in the all-jet final state in pp collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A measurement of the production cross section of top quark pairs in association with two b jets ($\mathrm{t\bar{t}}\mathrm{b\bar{b}}$) is presented using data collected in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS detector at the LHC corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The cross section is measured in the all-jet decay channel of the top quark pair by selecting events containing at least eight jets, of which at least two are identified as originating from the hadronization of b quarks. A combination of multivariate analysis techniques is used to reduce the large background from multijet events not containing a top quark pair, and to help discriminate between jets originating from top quark decays and other additional jets. The cross section is determined for the total phase space to be 5.5 $\pm$ 0.3 (stat)${}^{+1.6}_{-1.3}$ (syst) pb and also measured for two fiducial $\mathrm{t\bar{t}}\mathrm{b\bar{b}}$ definitions. The measured cross sections are found to be larger than theoretical predictions by a factor of 1.5-2.4, corresponding to 1-2 standard deviations.

[44] Measurement of B$^0_\mathrm{s}$ meson production in pp and PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The production cross sections of Bs0 mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel Bs0→J/ψϕ→μ+μ−K+K− at a center-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range |y|<2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum ( pT ) of the Bs0 mesons in the range of 7 to 50 GeV/ c and is compared to the predictions of perturbative QCD calculations. The Bs0 production yield in PbPb collisions is measured in two pT intervals, 7 to 15 and 15 to 50 GeV/ c , and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor ( RAA ) is found to be 1.5±0.6(stat)±0.5(syst) for 7–15 GeV/ c , and 0.87±0.30(stat)±0.17(syst) for 15–50 GeV/ c , respectively. Within current uncertainties, the Bs0 results are consistent with models of strangeness enhancement, and suppression by parton energy loss, as observed for the B+ mesons.

DOI : 10.1016/j.physletb.2019.07.014

[43] A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at a center-of-mass energy s=13TeV , collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.15 and 0.39 fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits.

DOI : 10.1016/j.physletb.2019.07.013

[42] Search for electroweak production of a vector-like T quark using fully hadronic final states

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is performed for electroweak production of a vector-like top quark partner T of charge 2/3 in association with a top or bottom quark, using proton-proton collision data at $\sqrt{s} =$ 13 TeV collected by the CMS experiment at the LHC in 2016. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The search targets T quarks over a wide range of masses and fractional widths, decaying to a top quark and either a Higgs boson or a Z boson in fully hadronic final states. The search is performed using two experimentally distinct signatures that depend on whether or not each quark from the decays of the top quark, Higgs boson, or Z boson produces an individual resolved jet. Jet substructure, b tagging, and kinematic variables are used to identify the top quark and boson jets, and also to suppress the standard model backgrounds. The data are found to be consistent with the expected backgrounds. Upper limits at 95% confidence level are set on the cross sections for T quark-mediated production of tHQq, tZQq, and their sum, where Q is the associated top or bottom heavy quark and q is another associated quark. The limits are given for each search signature for various T quark widths up to 30% of the T quark mass, and are between 2 pb and 20 fb for T quark masses in the range 0.6-2.6 TeV. These results are significantly more sensitive than prior searches for electroweak single production of T$\to$tH and represent the first constraints on T$\to$tZ using hadronic decays of the Z boson with this production mode.

[41] Search for low mass vector resonances decaying into quark-antiquark pairs in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for low mass narrow vector resonances decaying into quark-antiquark pairs is presented. The analysis is based on data collected in 2017 with the CMS detector at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 41.1 fb$^{-1}$. The results of this analysis are combined with those of an earlier analysis based on data collected at the same collision energy in 2016, corresponding to 35.9 fb$^{-1}$. Signal candidates will be recoiling against initial state radiation and are identified as energetic, large-radius jets with two pronged substructure. The invariant jet mass spectrum is probed for a potential narrow peaking signal over a smoothly falling background. No evidence for such resonances is observed within the mass range of 50-450 GeV. Upper limits at the 95% confidence level are set on the coupling of narrow resonances to quarks, as a function of the resonance mass. For masses between 50 and 300 GeV these are the most sensitive limits to date. This analysis extends the earlier search to a mass range of 300-450 GeV, which is probed for the first time with jet substructure techniques.

[40] Measurements of differential Z boson production cross sections in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Measurements are presented of the differential cross sections for Z bosons produced in proton-proton collisions at $\sqrt{s} =$ 13 TeV and decaying to muons and electrons. The data analyzed were collected in 2016 with the CMS detector at the LHC and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The measured fiducial inclusive product of cross section and branching fraction agrees with next-to-next-to-leading order quantum chromodynamics calculations. Differential cross sections of the transverse momentum $p_\mathrm{T}$, the optimized angular variable $\phi^*_\eta$, and the rapidity of lepton pairs are measured. The data are corrected for detector effects and compared to theoretical predictions using fixed order, resummed, and parton shower calculations. The uncertainties of the measured normalized cross sections are smaller than 0.5% for $\phi^*_\eta <$ 0.5 and for $p_\mathrm{T}^\mathrm{Z} <$ 50 GeV.

[39] Searches for physics beyond the standard model with the $M_\mathrm{T2}$ variable in hadronic final states with and without disappearing tracks in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 137 fb$^{-1}$. The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable $M_\mathrm{T2}$ for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving $R$-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.

[38] Search for vector-like leptons in multilepton final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for vectorlike leptons in multilepton final states is presented. The data sample corresponds to an integrated luminosity of 77.4  fb-1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016 and 2017. Events are categorized by the multiplicity of electrons, muons, and hadronically decaying τ leptons. The missing transverse momentum and the scalar sum of the lepton transverse momenta are used to distinguish the signal from background. The observed results are consistent with the expectations from the standard model hypothesis. The existence of a vectorlike lepton doublet, coupling to the third-generation standard model leptons in the mass range of 120–790 GeV, is excluded at 95% confidence level. These are the most stringent limits yet on the production of a vectorlike lepton doublet, coupling to the third-generation standard model leptons.

DOI : 10.1103/PhysRevD.100.052003

[37] Search for supersymmetry with a compressed mass spectrum in the vector boson fusion topology with 1-lepton and 0-lepton final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for supersymmetric particles produced in the vector boson fusion topology in proton-proton collisions is presented. The search targets final states with one or zero leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ of proton-proton collisions at $ \sqrt{s} $ = 13 TeV collected in 2016 with the CMS detector at the LHC. The observed dijet invariant mass and lepton-neutrino transverse mass spectra are found to be consistent with the standard model predictions. Upper limits are set on the cross sections for chargino $ \left({\tilde{\upchi}}_1^{\pm}\right) $ and neutralino $ \left({\tilde{\upchi}}_2^0\right) $ production with two associated jets. For a compressed mass spectrum scenario in which the $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ decays proceed via a light slepton and the mass difference between the lightest neutralino $ {\tilde{\upchi}}_1^0 $ and the mass-degenerate particles $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ is 1 (30) GeV, the most stringent lower limit to date of 112 (215) GeV is set on the mass of these latter two particles.

DOI : 10.1007/JHEP08(2019)150

[36] Search for a charged Higgs boson decaying into top and bottom quarks in proton-proton collisions at $\sqrt{s}=$ 13 TeV in events with electrons or muons

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is presented for a charged Higgs boson heavier than the top quark, produced in association with a top quark, or with a top and a bottom quark, and decaying into a top-bottom quark-antiquark pair. The search is performed using proton-proton collision data collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Events are selected by the presence of a single isolated charged lepton (electron or muon) or an opposite-sign dilepton (electron or muon) pair, categorized according to the jet multiplicity and the number of jets identified as originating from b quarks. Multivariate analysis techniques are used to enhance the discrimination between signal and background in each category. The data are compatible with the standard model, and 95% confidence level upper limits of 9.6-0.01 pb are set on the charged Higgs boson production cross section times branching fraction to a top-bottom quark-antiquark pair, for charged Higgs boson mass hypotheses ranging from 200 GeV to 3 TeV. The upper limits are interpreted in different minimal supersymmetric extensions of the standard model.

[35] Search for supersymmetry using Higgs boson to diphoton decays at $\sqrt{s}$ = 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for supersymmetry (SUSY) is presented where at least one Higgs boson is produced and decays to two photons in the decay chains of pair-produced SUSY particles. Two complementary analysis strategies are pursued: one focused on strong SUSY production and the other focused on electroweak SUSY production. The presence of charged leptons, additional Higgs boson candidates, and various kinematic variables are used to categorize events into search regions that are sensitive to different SUSY scenarios. The results are based on data from proton-proton collisions at the Large Hadron Collider at a center-of-mass energy of 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 77.5 fb$^{-1}$. No statistically significant excess of events is observed relative to the standard model expectations. We exclude bottom squark pair production for bottom squark masses below 530 GeV and a lightest SUSY particle mass of 1 GeV; wino-like chargino-neutralino production for chargino and neutralino masses below 235 GeV with a gravitino mass of 1 GeV; and higgsino-like chargino-neutralino production in the case where the neutralino decays exclusively to a Higgs boson and a gravitino for neutralino masses below 290 GeV.

[34] Measurement of exclusive $\rho(770)^0$ photoproduction in ultraperipheral pPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Exclusive ${{{\uprho _{}^{}} _{}^{}}{{\left( {770}\right) }{}_{}^{}}} ^{0}$ photoproduction is measured for the first time in ultraperipheral pPb collisions at $\sqrt{\smash [b]{s_{_{\mathrm {NN}}}}} = 5.02\,\text {Te}\text {V} $ with the CMS detector. The cross section $\sigma ({\upgamma _{}^{}} \mathrm{p}\rightarrow {{{\uprho _{}^{}} _{}^{}}{{\left( {770}\right) }{}_{}^{}}} ^{0}\mathrm{p})$ is $11.0 \pm 1.4\,\text {(stat)} \pm 1.0\,\text {(syst)} $ $\mu $ b at $\langle W_{{\upgamma _{}^{}} \mathrm{p}}\rangle = 92.6\,\text {Ge}\text {V} $ for photon–proton centre-of-mass energies $W_{{\upgamma _{}^{}} \mathrm{p}}$ between 29 and $213\,\text {Ge}\text {V} $ . The differential cross section $\mathrm {d}\sigma /\mathrm {d}|t |$ is measured in the interval $0.025< |t | < 1\,\text {Ge}\text {V} ^{2}$ as a function of $W_{{\upgamma _{}^{}} \mathrm{p}}$ , where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section $\sigma ({\upgamma _{}^{}} \mathrm{p}\rightarrow {{{\uprho _{}^{}} _{}^{}}{{\left( {770}\right) }{}_{}^{}}} ^{0}\mathrm{p})$ has a power-law dependence on the photon–proton centre-of-mass, consistent with electron–proton collision measurements performed at HERA. The $W_{{\upgamma _{}^{}} \mathrm{p}}$ dependence of the exponential slope of the differential cross section $\mathrm {d}\sigma /\mathrm {d}|t |$ is also measured.

DOI : 10.1140/epjc/s10052-019-7202-9

[33] Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The standard model (SM) production of four top quarks ($\mathrm{t\bar{t}t\bar{t}}$) in proton-proton collision is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 fb$^{-a}$ at a center-of-mass energy of 13 TeV. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $\mathrm{t\bar{t}t\bar{t}}$ signal are respectively 2.6 and 2.7 standard deviations, and the $\mathrm{t\bar{t}t\bar{t}}$ cross section is measured to be 12.6$^{+5.8}_{-5.2}$ fb. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $y_{\mathrm{t}}$, yielding a limit of $|{y_{\mathrm{t}}/y_{\mathrm{t}}^{\mathrm{SM}}}| <$ 1.7 at 95% confidence level, where $y_{\mathrm{t}}^{\mathrm{SM}}$ is the SM value of $y_{\mathrm{t}}$. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $\hat{H}<0.12$. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 GeV and 350-550 GeV for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

[32] Search for dark matter in events with a leptoquark and missing transverse momentum in proton-proton collisions at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search is presented for dark matter in proton-proton collisions at a center-of-mass energy of s=13 TeV using events with at least one high transverse momentum ( pT ) muon, at least one high- pT jet, and large missing transverse momentum. The data were collected with the CMS detector at the CERN LHC in 2016 and 2017, and correspond to an integrated luminosity of 77.4 fb −1 . In the examined scenario, a pair of scalar leptoquarks is assumed to be produced. One leptoquark decays to a muon and a jet while the other decays to dark matter and low- pT standard model particles. The signature for signal events would be significant missing transverse momentum from the dark matter in conjunction with a peak at the leptoquark mass in the invariant mass distribution of the highest pT muon and jet. The data are observed to be consistent with the background predicted by the standard model. For the first benchmark scenario considered, dark matter masses up to 500 GeV are excluded for leptoquark masses mLQ≈1400 GeV, and up to 300 GeV for mLQ≈1500 GeV. For the second benchmark scenario, dark matter masses up to 600 GeV are excluded for mLQ≈1400 GeV.

DOI : 10.1016/j.physletb.2019.05.046

[31] Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two muons and two b quarks in pp collisions at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for exotic decays of the Higgs boson to a pair of light pseudoscalar particles a1 is performed under the hypothesis that one of the pseudoscalars decays to a pair of opposite sign muons and the other decays to bb‾ . Such signatures are predicted in a number of extensions of the standard model (SM), including next-to-minimal supersymmetry and two-Higgs-doublet models with an additional scalar singlet. The results are based on a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb−1 , accumulated with the CMS experiment at the CERN LHC in 2016 at a centre-of-mass energy of 13 TeV. No statistically significant excess is observed with respect to the SM backgrounds in the search region for pseudoscalar masses from 20 GeV to half of the Higgs boson mass. Upper limits at 95% confidence level are set on the product of the production cross section and branching fraction, σhB(h→a1a1→μ+μ−bb‾) , ranging from 5 to 33 fb, depending on the pseudoscalar mass. Corresponding limits on the branching fraction, assuming the SM prediction for σh , are (1–7)×10−4 .

DOI : 10.1016/j.physletb.2019.06.021

[30] Measurement of electroweak WZ boson production and search for new physics in WZ + two jets events in pp collisions at $\sqrt{s} =$ 13TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A measurement of WZ electroweak (EW) vector boson scattering is presented. The measurement is performed in the leptonic decay modes WZ→ℓνℓ′ℓ′ , where ℓ,ℓ′=e,μ . The analysis is based on a data sample of proton-proton collisions at s=13 TeV at the LHC collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb −1 . The WZ plus two jet production cross section is measured in fiducial regions with enhanced contributions from EW production and found to be consistent with standard model predictions. The EW WZ production in association with two jets is measured with an observed (expected) significance of 2.2 (2.5) standard deviations. Constraints on charged Higgs boson production and on anomalous quartic gauge couplings in terms of dimension-eight effective field theory operators are also presented.

DOI : 10.1016/j.physletb.2019.05.042

[29] Search for dark matter particles produced in association with a Higgs boson in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for dark matter (DM) particles is performed using events with a Higgs boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The search is performed in five Higgs boson decay channels: h$ \to \mathrm{b\bar{b}}$, $\gamma\gamma$, $\tau^{+}\tau^{-}$, W$^{+}$W$^{-}$, and ZZ and the results from the individual channels are combined to maximize the sensitivity of the analysis. No significant excess over the expected standard model background is observed in any of the five channels or in their combination. Limits are set on DM production in the context of two simplified models. The results are also interpreted in terms of a spin-independent DM-nucleon scattering cross section and compared to those from direct-detection DM experiments. This is the first search for DM particles produced in association with a Higgs boson decaying to a pair of W or Z bosons, and the first statistical combination based on five Higgs boson decay channels.

[28] Centrality and pseudorapidity dependence of the transverse energy density in pPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The almost hermetic coverage of the CMS detector is used to measure the distribution of transverse energy, ET, over 13.2 units of pseudorapidity, η, for pPb collisions at a center-of-mass energy per nucleon pair of sNN=5.02TeV. The huge angular acceptance exploits the fact that the CASTOR calorimeter at −6.6<η<−5.2 is effectively present on both sides of the colliding system because of a switch in the proton-going and lead-going beam directions. This wide acceptance enables the study of correlations between well-separated angular regions and makes the measurement a particularly powerful test of event generators. For minimum bias pPb collisions the maximum value of dET/dη is 22GeV, which implies an ET per participant nucleon pair comparable to that of peripheral PbPb collisions at sNN=2.76TeV. The increase of dET/dη with centrality is much stronger for the lead-going side than for the proton-going side. The η dependence of dET/dη is sensitive to the η range in which the centrality variable is defined. Several modern generators are compared to these results but none is able to capture all aspects of the η and centrality dependence of the data and the correlations observed between different η regions.

DOI : 10.1103/PhysRevC.100.024902

[27] Search for heavy Higgs bosons decaying to a top quark pair in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is presented for additional scalar (H) or pseudoscalar (A) Higgs bosons decaying to a top quark pair in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set analyzed corresponds to an integrated luminosity of 35.9 fb$^{-1}$ collected by the CMS experiment at the LHC. Final states with one or two charged leptons are considered. The invariant mass of the reconstructed top quark pair system and variables that are sensitive to the spin of the particles decaying into the top quark pair are used to search for signatures of the H or A bosons. The interference with the standard model top quark pair background is taken into account. A moderate signal-like deviation compatible with an A boson with a mass of 400 GeV is observed with a global significance of 1.9 standard deviations. New stringent constraints are reported on the strength of the coupling of the hypothetical bosons to the top quark, with the mass of the bosons ranging from 400 to 750 GeV and their total relative width from 0.5 to 25%. The results of the search are also interpreted in a minimal supersymmetric standard model scenario. Values of $m_\mathrm{A}$ from 400 to 700 GeV are probed, and a region with values of $\tan\beta$ below 1.0 to 1.5, depending on $m_\mathrm{A}$, is excluded at 95% confidence level.

[26] Search for the production of W$^\pm$W$^\pm$W$^\mp$ events at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for the production of events containing three W bosons predicted by the standard model is reported. The search is based on a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the CERN LHC and corresponding to a total integrated luminosity of 35.9  fb-1. The search is performed in final states with three leptons (electrons or muons), or with two same-charge leptons plus two jets. The observed (expected) significance of the signal for W±W±W∓ production is 0.60 (1.78) standard deviations, and the ratio of the measured signal yield to that expected from the standard model is 0.34-0.34+0.62. Limits are placed on three anomalous quartic gauge couplings and on the production of massive axionlike particles.

DOI : 10.1103/PhysRevD.100.012004

[25] Search for charged Higgs bosons in the H$^{\pm}$ $\to$ $\tau^{\pm}\nu_\tau$ decay channel in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search is presented for charged Higgs bosons in the H$^{±}$ → τ$^{±}$ν$_{τ}$ decay mode in the hadronic final state and in final states with an electron or a muon. The search is based on proton-proton collision data recorded by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The results agree with the background expectation from the standard model. Upper limits at 95% confidence level are set on the production cross section times branching fraction to τ$^{±}$ν$_{τ}$ for an H$^{±}$ in the mass range of 80GeV to 3TeV, including the region near the top quark mass. The observed limit ranges from 6 pb at 80 GeV to 5 fb at 3 TeV. The limits are interpreted in the context of the minimal supersymmetric standard model m$_{h}^{hod −}$ scenario.

DOI : 10.1007/JHEP07(2019)142

[24] Measurement of differential cross sections and charge ratios for $t$-channel single top quark production in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A measurement is presented of differential cross sections for $t$-channel single top quark and antiquark production in proton-proton collisions at a centre-of-mass energy of 13 TeV by the CMS experiment at the LHC. From a data set corresponding to an integrated luminosity of 35.9 fb$^{-1}$, events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum ($p_\mathrm{T}$), rapidity, and polarisation angle, the charged lepton $p_\mathrm{T}$ and rapidity, and the $p_\mathrm{T}$ of the W boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and W boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be 0.439 $\pm$ 0.062, in agreement with the standard model prediction.

[23] Search for anomalous triple gauge couplings in WW and WZ production in lepton + jet events in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search is presented for three additional operators that would lead to anomalousWW$\gamma$ or WWZ couplings with respect to those in the standard model. They are constrained by studying events with two vector bosons; a W boson decaying to e$\nu$ or $\mu\nu$, and a W or Z boson decaying hadronically, reconstructed as a single, massive, large-radius jet. The search uses a data set of proton-proton collisions at a centre-of-mass energy of 13 TeV, recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Using the reconstructed diboson invariant mass, 95% confidence intervals are obtained for the anomalous coupling parameters of $-$1.58 $< c_\mathrm{WWW}/\Lambda^2 <$ 1.59 TeV$^{-2}$, $-$2.00 $< c_\mathrm{W}/\Lambda^2 <$ 2.65 TeV$^{-2}$, and $-$8.78$ < c_\mathrm{B}/\Lambda^2 <$ 8.54 TeV$^{-2}$, in agreement with standard model expectations of zero for each parameter. These are the strictest bounds on these parameters to date.

[22] Search for physics beyond the standard model in events with overlapping photons and jets

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

Results are reported from a search for new particles that decay into a photon and two gluons, in events with jets. Novel jet substructure techniques are developed that allow photons to be identified in an environment densely populated with hadrons. The analyzed proton-proton collision data were collected by the CMS experiment at the LHC, in 2016 at $\sqrt{s} =$ 13 TeV, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The spectra of total transverse hadronic energy of candidate events are examined for deviations from the standard model predictions. No statistically significant excess is observed over the expected background. The first cross section limits on new physics processes resulting in such events are set. The results are interpreted as upper limits on the rate of gluino pair production, utilizing a simplified stealth supersymmetry model. The excluded gluino masses extend up to 1.7 TeV, for a neutralino mass of 200 GeV and exceed previous mass constraints set by analyses targeting events with isolated photons.

[21] Study of the B$^+ \to $J$/\psi\overline{\Lambda}$p decay in proton-proton collisions at $\sqrt{s}=$ 8 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A study of the B$^+\to $J$/\psi\overline{\Lambda}$p decay using proton-proton collision data collected at $\sqrt{s}=$ 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb$^{-1}$, is presented. The ratio of branching fractions $\mathcal{B}$(B$^+ \to $J$/\psi\overline{\Lambda}$p )$/\mathcal{B}$(B$^\to $J$/\psi$K$^*$(892)$^+$) is measured to be (1.054 $\pm$ 0.057 (stat) $\pm$ 0.035 (syst) $\pm$ 0.011 ($\mathcal{B}$))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of $\overline{\Lambda}$ and K$^*$(892)$^+$ decays to reconstructed final states. The invariant mass distributions of the J$/\psi\overline{\Lambda}$, J$/\psi$p, and $\overline{\Lambda}$p systems produced in the B$^+\to $J$/\psi\overline{\Lambda}$p decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the inclusion of contributions from excited kaons decaying to the $\overline{\Lambda}$p system improves the description of the observed invariant mass distributions.

[20] Studies of Beauty Suppression via Nonprompt $D^0$ Mesons in Pb-Pb Collisions at $Q^2 = 4$ $\rm GeV^2$

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The transverse momentum spectra of D0 mesons from b hadron decays are measured at midrapidity (|y|<1) in pp and Pb-Pb collisions at a nucleon-nucleon center of mass energy of 5.02 TeV with the CMS detector at the LHC. The D0 mesons from b hadron decays are distinguished from prompt D0 mesons by their decay topologies. In Pb-Pb collisions, the B→D0 yield is found to be suppressed in the measured pT range from 2 to 100  GeV/c as compared to pp collisions. The suppression is weaker than that of prompt D0 mesons and charged hadrons for pT around 10  GeV/c. While theoretical calculations incorporating partonic energy loss in the quark-gluon plasma can successfully describe the measured B→D0 suppression at higher pT, the data show an indication of larger suppression than the model predictions in the range of 2<pT<5  GeV/c.

DOI : 10.1103/PhysRevLett.123.022001

[19] Performance of missing transverse momentum reconstruction in proton-proton collisions at $\sqrt{s} =$ 13 TeV using the CMS detector

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

The performance of missing transverse momentum (Tmiss) reconstruction algorithms for the CMS experiment is presented, using proton-proton collisions at a center-of-mass energy of 13 TeV, collected at the CERN LHC in 2016. The data sample corresponds to an integrated luminosity of 35.9 fb-1. The results include measurements of the scale and resolution of Tmiss, and detailed studies of events identified with anomalous Tmiss. The performance is presented of a Tmiss reconstruction algorithm that mitigates the effects of multiple proton-proton interactions, using the "pileup per particle identification" method. The performance is shown of an algorithm used to estimate the compatibility of the reconstructed Tmiss with the hypothesis that it originates from resolution effects.

DOI : 10.1088/1748-0221/14/07/P07004

[18] Search for a heavy pseudoscalar boson decaying to a Z and a Higgs boson at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search is presented for a heavy pseudoscalar boson $\text {A}$ decaying to a Z  boson and a Higgs boson with mass of 125 $\,\text {GeV}$ . In the final state considered, the Higgs boson decays to a bottom quark and antiquark, and the Z  boson decays either into a pair of electrons, muons, or neutrinos. The analysis is performed using a data sample corresponding to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ collected in 2016 by the CMS experiment at the LHC from proton–proton collisions at a center-of-mass energy of 13 $\,\text {Te}\text {V}$ . The data are found to be consistent with the background expectations. Exclusion limits are set in the context of two-Higgs-doublet models in the $\text {A}$ boson mass range between 225 and 1000 $\,\text {GeV}$ .

DOI : 10.1140/epjc/s10052-019-7058-z

[17] Combined search for supersymmetry with photons in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A combination of four searches for new physics involving signatures with at least one photon and large missing transverse momentum, motivated by generalized models of gauge-mediated supersymmetry (SUSY) breaking, is presented. All searches make use of proton-proton collision data at $\sqrt{s}=$ 13 TeV, which were recorded with the CMS detector at the LHC in 2016, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. Signatures with at least one photon and large missing transverse momentum are categorized into events with two isolated photons, events with a lepton and a photon, events with additional jets, and events with at least one high-energy photon. No excess of events is observed beyond expectations from standard model processes, and limits are set in the context of gauge-mediated SUSY. Compared to the individual searches, the combination extends the sensitivity to gauge-mediated SUSY in both electroweak and strong production scenarios by up to 100 GeV in neutralino and chargino masses, and yields the first CMS result combining various SUSY searches in events with photons at $\sqrt{s}=$ 13 TeV.

[16] Search for supersymmetry in final states with photons and missing transverse momentum in proton-proton collisions at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Results are reported of a search for supersymmetry in final states with photons and missing transverse momentum in proton-proton collisions at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ collected at a center-of-mass energy of 13 TeV using the CMS detector. The results are interpreted in the context of models of gauge-mediated supersymmetry breaking. Production cross section limits are set on gluino and squark pair production in this framework. Gluino masses below 1.86 TeV and squark masses below 1.59 TeV are excluded at 95% confidence level.

DOI : 10.1007/JHEP06(2019)143

[15] An embedding technique to determine $\tau\tau$ backgrounds in proton-proton collision data

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

An embedding technique is presented to estimate standard model ττ backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed μμ events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS . Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at √s=13 TeV corresponding to an integrated luminosity of 41.5 fb−1.

DOI : 10.1088/1748-0221/14/06/P06032

[14] Search for the associated production of the Higgs boson and a vector boson in proton-proton collisions at $\sqrt{s}=$ 13 TeV via Higgs boson decays to $\tau$ leptons

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to a pair of τ leptons is performed. A data sample of proton-proton collisions collected at $ \sqrt{s} $ = 13 TeV by the CMS experiment at the CERN LHC is used, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The signal strength is measured relative to the expectation for the standard model Higgs boson, yielding μ = 2.5$_{− 1.3}^{+ 1.4}$ . These results are combined with earlier CMS measurements targeting Higgs boson decays to a pair of τ leptons, performed with the same data set in the gluon fusion and vector boson fusion production modes. The combined signal strength is μ = 1.24$_{− 0.27}^{+ 0.29}$ (1.00$_{− 0.23}^{+ 0.24}$ expected), and the observed significance is 5.5 standard deviations (4.8 expected) for a Higgs boson mass of 125 GeV.

DOI : 10.1007/JHEP06(2019)093

[13] A multi-dimensional search for new heavy resonances decaying to boosted WW, WZ, or ZZ boson pairs in the dijet final state at 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search in an all-jet final state for new massive resonances decaying to WW, WZ, or ZZ boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb$^{-1}$ recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13 TeV. The search is focussed on potential resonances with masses above 1.2 TeV, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1 Z' and W' resonances with masses below 3.5 and 3.8 TeV, respectively, are excluded at 95% confidence level. In a narrow-width bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2 TeV, respectively. The limits presented in this paper are the best to date in the dijet final state.

[12] Measurements of the Higgs boson width and anomalous $HVV$ couplings from on-shell and off-shell production in the four-lepton final state

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Studies of on-shell and off-shell Higgs boson production in the four-lepton final state are presented, using data from the CMS experiment at the LHC that correspond to an integrated luminosity of 80.2  fb-1 at a center-of-mass energy of 13 TeV. Joint constraints are set on the Higgs boson total width and parameters that express its anomalous couplings to two electroweak vector bosons. These results are combined with those obtained from the data collected at center-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7  fb-1, respectively. Kinematic information from the decay particles and the associated jets are combined using matrix element techniques to identify the production mechanism and to increase sensitivity to the Higgs boson couplings in both production and decay. The constraints on anomalous HVV couplings are found to be consistent with the standard model expectation in both the on-shell and off-shell regions. Under the assumption of a coupling structure similar to that in the standard model, the Higgs boson width is constrained to be 3.2-2.2+2.8  MeV while the expected constraint based on simulation is 4.1-4.0+5.0  MeV. The constraints on the width remain similar with the inclusion of the tested anomalous HVV interactions.

DOI : 10.1103/PhysRevD.99.112003

[11] Search for invisible decays of a Higgs boson produced through vector boson fusion in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

A search for invisible decays of a Higgs boson is performed using proton-proton collision data collected with the CMS detector at the LHC in 2016 at a center-of-mass energy s=13TeV , corresponding to an integrated luminosity of 35.9 fb−1 . The search targets the production of a Higgs boson via vector boson fusion. The data are found to be in agreement with the background contributions from standard model processes. An observed (expected) upper limit of 0.33 (0.25), at 95% confidence level, is placed on the branching fraction of the Higgs boson decay to invisible particles, assuming standard model production rates and a Higgs boson mass of 125.09 GeV. Results from a combination of this analysis and other direct searches for invisible decays of the Higgs boson, performed using data collected at s=7 , 8, and 13 TeV, are presented. An observed (expected) upper limit of 0.19 (0.15), at 95% confidence level, is set on the branching fraction of invisible decays of the Higgs boson. The combined limit represents the most stringent bound on the invisible branching fraction of the Higgs boson reported to date. This result is also interpreted in the context of Higgs-portal dark matter models, in which upper bounds are placed on the spin-independent dark-matter-nucleon scattering cross section.

DOI : 10.1016/j.physletb.2019.04.025

[10] 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

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

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.

DOI : 10.1016/j.physletb.2019.03.064

[9] Production of $\Lambda_\mathrm{c}^+$ baryons in proton-proton and lead-lead collisions at $\sqrt{s_\mathrm{NN}}=$ 5.02 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; T. Bergauer  et al.

The differential cross sections of $\Lambda_\mathrm{c}^+$ baryon production are measured via the exclusive decay channel $\Lambda_\mathrm{c}^+ \to $pK$^-\pi^+$, as a function of transverse momentum ($p_\mathrm{T}$) in proton-proton (pp) and lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with the CMS detector at the LHC. The measurement is performed within the $\Lambda_\mathrm{c}^+$ rapidity interval $|y|<$1.0 in the $p_\mathrm{T}$ range of 5-20 GeV/$c$ in pp and 10-20 GeV/$c$ in PbPb collisions. The observed yields of $\Lambda_\mathrm{c}^+$ for $p_\mathrm{T}$ of 10-20 GeV/$c$ suggest a possible suppression in central PbPb collisions compared to pp collisions. The $\Lambda_\mathrm{c}^+/$D$^0$ production ratio in pp collisions is compared to theoretical models. In PbPb collisions, this ratio is consistent with the result from pp collisions in their common $p_\mathrm{T}$ range.

[8] Search for a low-mass $\tau^+\tau^-$ resonance in association with a bottom quark in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A general search is presented for a low-mass τ$^{−}$τ$^{+}$ resonance produced in association with a bottom quark. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. The data are consistent with the standard model expectation. Upper limits at 95% confidence level on the cross section times branching fraction are determined for two signal models: a light pseudoscalar Higgs boson decaying to a pair of τ leptons produced in association with bottom quarks, and a low-mass boson X decaying to a τ-lepton pair that is produced in the decay of a bottom-like quark B such that B → bX. Masses between 25 and 70 GeV are probed for the light pseudoscalar boson with upper limits ranging from 250 to 44 pb. Upper limits from 20 to 0.3 pb are set on B masses between 170 and 450 GeV for X boson masses between 20 and 70 GeV.

DOI : 10.1007/JHEP05(2019)210

[7] Search for supersymmetry in events with a photon, jets, $\mathrm {b}$ -jets, and missing transverse momentum in proton–proton collisions at 13 $\,\text {Te}\text {V}$

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for supersymmetry is presented based on events with at least one photon, jets, and large missing transverse momentum produced in proton–proton collisions at a center-of-mass energy of 13 $\,\text {Te}\text {V}$ . The data correspond to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of $\mathrm {b}$ -tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, the production of gluinos with masses as large as 2120 $\,\text {Ge}\text {V}$ and the production of top squarks with masses as large as 1230 $\,\text {Ge}\text {V}$ are excluded at 95% confidence level.

DOI : 10.1140/epjc/s10052-019-6926-x

[6] Correlations of azimuthal anisotropy Fourier harmonics in pPb collisions at $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Event-by-event correlations of azimuthal anisotropy Fourier coefficients ($v_n$) in 8.16 TeV pPb collision data, collected by the CMS experiment at the LHC, are extracted using a subevent four-particle cumulant technique. The pseudorapidity range of the CMS tracker from $-$2.4 to 2.4 is divided into either two, three, or four distinct subevent regions. Each combination of four particles constructed from tracks with transverse momentum between 0.3 and 3.0 GeV is then analyzed in terms of how the particles populate the subevents. Using the subevent technique, correlations between $v_n$ of different orders are measured as functions of particle multiplicity and compared to the standard cumulant method without subevents. At high multiplicity, the $v_2$ and $v_3$ coefficients exhibit an anticorrelation; this behavior is observed consistently using various methods. The $v_2$ and $v_4$ correlation strength is found to depend on the number of subevents used in the calculation. At low-multiplicities, the results from different methods diverge because of different contributions of few-particle correlations. These findings significantly lower the multiplicity range that was previously established for the onset of collective behavior in small systems.

[5] Search for associated production of a Higgs boson and a single top quark in proton-proton collisions at $\sqrt{s} =$ TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search is presented for the production of a Higgs boson in association with a single top quark, based on data collected in 2016 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of 35.9  fb-1. The production cross section for this process is highly sensitive to the absolute values of the top quark Yukawa coupling, yt; the Higgs boson coupling to vector bosons, gHVV; and, uniquely, their relative sign. Analyses using multilepton signatures, targeting H→WW, H→ττ, and H→ZZ decay modes, and signatures with a single lepton and a bb¯ pair, targeting the H→bb¯ decay, are combined with a reinterpretation of a measurement in the H→γγ channel to constrain yt. For a standard model–like value of gHVV, the data favor positive values of yt and exclude values of yt below about -0.9ytSM.

DOI : 10.1103/PhysRevD.99.092005

[4] Combined measurements of Higgs boson couplings in proton–proton collisions at $\sqrt{s}=13\,\text {Te}\text {V} $

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton–proton collision data set recorded with the CMS detector in 2016 at $\sqrt{s}=13\,\text {Te}\text {V} $ , corresponding to an integrated luminosity of 35.9 ${\,\text {fb}^{-1}} $ . The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a $\mathrm {W}$ or $\mathrm {Z}$ boson, or a top quark-antiquark pair) and the following decay modes: $\mathrm {H} \rightarrow \gamma \gamma $ , $\mathrm {Z}\mathrm {Z}$ , $\mathrm {W}\mathrm {W}$ , $\mathrm {\tau }\mathrm {\tau }$ , $\mathrm {b} \mathrm {b} $ , and $\mathrm {\mu }\mathrm {\mu }$ . Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be $\mu =1.17\pm 0.10$ , assuming a Higgs boson mass of $125.09\,\text {Ge}\text {V} $ . Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.

DOI : 10.1140/epjc/s10052-019-6909-y

[3] Combinations of single-top-quark production cross-section measurements and |f$_{LV}$V$_{tb}$| determinations at $ \sqrt{s} $ = 7 and 8 TeV with the ATLAS and CMS experiments

M. Aaboud; G. Aad; B. Abbott; D. C. Abbott; O. Abdinov  et al.

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.

DOI : 10.1007/JHEP05(2019)088

[2] Search for a W' boson decaying to a $\tau$ lepton and a neutrino in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for a new high-mass resonance decaying to a τ lepton and a neutrino is reported. The analysis uses proton-proton collision data collected by the CMS experiment at the LHC at s=13TeV , corresponding to an integrated luminosity of 35.9 fb−1 . The search utilizes hadronically decaying τ leptons. No excess in the event yield is observed at high transverse masses of the τ and missing transverse momentum. An interpretation of results within the sequential standard model excludes W′ boson masses below 4.0 TeV at 95% confidence level. Existing limits are also improved on models in which the W′ boson decays preferentially to fermions of the third generation. Heavy W′ bosons with masses less than 1.7–3.9 TeV, depending on the coupling in the non-universal G(221) model, are excluded at 95% confidence level. These are the most stringent limits on this model to date.

DOI : 10.1016/j.physletb.2019.01.069

[1] Search for an $L_{\mu}-L_{\tau}$ gauge boson using Z$\to4\mu$ events in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A. M. Sirunyan; A. Tumasyan; W. Adam; F. Ambrogi; E. Asilar  et al.

A search for a narrow Z′ gauge boson with a mass between 5 and 70 GeV resulting from an Lμ−Lτ U(1) local gauge symmetry is reported. Theories that predict such a particle have been proposed as an explanation of various experimental discrepancies, including the lack of a dark matter signal in direct-detection experiments, tension in the measurement of the anomalous magnetic moment of the muon, and reports of possible lepton flavor universality violation in B meson decays. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV is used, corresponding to an integrated luminosity of 77.3 fb −1 recorded in 2016 and 2017 by the CMS detector at the LHC. Events containing four muons with an invariant mass near the standard model Z boson mass are analyzed, and the selection is further optimized to be sensitive to the events that may contain Z→Z′μμ→4μ decays. The event yields are consistent with the standard model predictions. Upper limits of 10−8 – 10−7 at 95% confidence level are set on the product of branching fractions B(Z→Z′μμ)B(Z′→μμ) , depending on the Z′ mass, which excludes a Z′ boson coupling strength to muons above 0.004–0.3. These are the first dedicated limits on Lμ−Lτ models at the LHC and result in a significant increase in the excluded model parameter space. The results of this search may also be used to constrain the coupling strength of any light Z′ gauge boson to muons.

DOI : 10.1016/j.physletb.2019.01.072