Publications
1342 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of single-diffractive dijet production in proton-proton collisions at √<i>s</i> = 8 TeV with the CMS and TOTEM experiments (vol 80, 1164, 2020), EUROPEAN PHYSICAL JOURNAL C, Vol: 81, ISSN: 1434-6044
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Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Angular analysis of the decay B+-> K*(892)(+)mu(+)mu(-) in proton-proton collisions at root s=8 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-35, ISSN: 1029-8479
Angular distributions of the decay B+ → K∗(892)+μ+μ− are studied using events collected with the CMS detector in s√ = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb−1. The forward-backward asymmetry of the muons and the longitudinal polarization of the K∗(892)+ meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for supersymmetry in final states with two oppositely charged same-flavor leptons and missing transverse momentum in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-62, ISSN: 1029-8479
A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data sample of proton-proton collisions at s√ = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass; a kinematic edge in the invariant mass distribution of the lepton pair; and the nonresonant production of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1870 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for dark matter produced in association with avleptonically decaying Z boson in proton-proton collisions at root s = 13 TeV (vol 81, 13, 2021), European Physical Journal C: Particles and Fields, Vol: 81, ISSN: 1124-1861
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the Higgs boson production rate in association with top quarks in final states with electrons, muons, and hadronically decaying tau leptons at s√=13TeV, The European Physical Journal C, Vol: 81, Pages: 1-51, ISSN: 1434-6044
The rate for Higgs (H) bosons production in association with either one (tH) or two (tt¯H) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton–proton collisions recorded at a center-of-mass energy of 13TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137fb−1. The analysis is aimed at events that contain H→WW, H→ττ, or H→ZZ decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among tH, tt¯H, and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the tt¯H and tH signals correspond to 0.92±0.19(stat)+0.17−0.13(syst) and 5.7±2.7(stat)±3.0(syst) of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for tt¯H, and to 1.4 (0.3) for tH production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling yt of the Higgs boson to the top quark divided by its SM expectation, κt=yt/ySMt, is constrained to be within −0.9<κt<−0.7 or 0.7<κt<1.1, at 95% confidence level. This result is the most sensitive measurement of the tt¯H production rate to date.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Development and validation of HERWIG 7 tunes from CMS underlying-event measurements, The European Physical Journal C, Vol: 81, Pages: 1-47, ISSN: 1434-6044
This paper presents new sets of parameters (“tunes”) for the underlying-event model of the HERWIG7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in HERWIG7, and are obtained from a fit to minimum-bias data collected by the CMS experiment at s√=0.9, 7, and 13TeV. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of differential cross sections for Z bosons produced in association with charm jets in pp collisions at s√ = 13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-41, ISSN: 1029-8479
Measurements are presented of differential cross sections for the production of Z bosons in association with at least one jet initiated by a charm quark in pp collisions at s√ = 13 TeV. The data recorded by the CMS experiment at the LHC correspond to an integrated luminosity of 35.9 fb−1. The final states contain a pair of electrons or muons that are the decay products of a Z boson, and a jet consistent with being initiated by a charm quark produced in the hard interaction. Differential cross sections as a function of the transverse momentum pT of the Z boson and pT of the charm jet are compared with predictions from Monte Carlo event generators. The inclusive production cross section 405.4 ± 5.6 (stat) ± 24.3 (exp) ± 3.7 (theo) pb, is measured in a fiducial region requiring both leptons to have pseudorapidity |η| < 2.4 and pT > 10 GeV, at least one lepton with pT > 26 GeV, and a mass of the pair in the range 71–111 GeV, while the charm jet is required to have pT > 30 GeV and |η| < 2.4. These are the first measurements of these cross sections in proton-proton collisions at 13 TeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for nonresonant Higgs boson pair production in final states with two bottom quarks and two photons in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-57, ISSN: 1029-8479
A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of s√ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into γγbb¯¯¯. The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κλ and the coupling between a pair of Higgs bosons and a pair of vector bosons c2V are constrained within the ranges −3.3 < κλ < 8.5 and −1.3 < c2V < 3.5 at 95% confidence level. Constraints on κλ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κλ and the top quark Yukawa coupling modifier κt.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of differential t(t)over-bar production cross sections using top quarks at large transverse momenta in pp collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 1-43, ISSN: 1550-2368
A measurement is reported of differential top quark pair (t¯t) production cross sections, where top quarks are produced at large transverse momenta. The data collected with the CMS detector at the LHC are from pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb−1. The measurement uses events where at least one top quark decays as t→Wb→q¯q′b and is reconstructed as a large-radius jet with transverse momentum in excess of 400 GeV. The second top quark is required to decay either in a similar way or leptonically, as inferred from a reconstructed electron or muon, a bottom quark jet, and missing transverse momentum due to the undetected neutrino. The cross section is extracted as a function of kinematic variables of individual top quarks or of the t¯t system. The results are presented at the particle level, within a region of phase space close to that of the experimental acceptance, and at the parton level and are compared to various theoretical models. In both decay channels, the observed absolute cross sections are significantly lower than the predictions from theory, while the normalized differential measurements are well described.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for new physics in top quark production with additional leptons in proton-proton collisions at root s=13 TeV using effective field theory, The Journal of High Energy Physics, Vol: 2021, Pages: 1-54, ISSN: 1029-8479
Events containing one or more top quarks produced with additional prompt leptons are used to search for new physics within the framework of an effective field theory (EFT). The data correspond to an integrated luminosity of 41.5 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, collected by the CMS experiment in 2017. The selected events are required to have either two leptons with the same charge or more than two leptons; jets, including identified bottom quark jets, are also required, and the selected events are divided into categories based on the multiplicities of these objects. Sixteen dimension-six operators that can affect processes involving top quarks produced with additional charged leptons are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A simultaneous fit of the 16 WCs to the data is performed and two standard deviation confidence intervals for the WCs are extracted; the standard model expectations for the WC values are within these intervals for all of the WCs probed.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the inclusive and differential Higgs boson production cross sections in the leptonic WW decay mode at p root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-48, ISSN: 1029-8479
Measurements of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at s√ = 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016–2018, corresponding to an integrated luminosity of 137 fb−1. Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jet multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86.5 ± 9.5 fb, consistent with the Standard Model expectation of 82.5 ± 4.2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of pp -> ZZ production cross sections and constraints on anomalous triple gauge couplings at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-30, ISSN: 1124-1861
The production of Z boson pairs in proton–proton (pp) collisions, pp→(Z/γ∗)(Z/γ∗)→2ℓ2ℓ′, where ℓ,ℓ′=e or μ, is studied at a center-of-mass energy of 13TeV with the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 137fb−1, collected during 2016–2018. The ZZ production cross section, σtot(pp→ZZ)=17.4±0.3(stat)±0.5(syst)±0.4(theo)±0.3(lumi) pb, measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region 60<mℓ+ℓ−<120GeV is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-43, ISSN: 1029-8479
A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb−1, recorded at a center-of-mass energy of 13 TeV in 2016–2018. 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 production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 813, Pages: 1-25, ISSN: 0370-2693
Measurements of the second Fourier harmonic coefficient (v2) of the azimuthal distributions of promptand nonprompt D0 mesons produced in pp and pPb collisions are presented. Nonprompt D0 mesons comefrom beauty hadron decays. The data samples are collected by the CMS experiment at nucleon-nucleoncenter-of-mass energies of 13 and 8.16 TeV, respectively. In high multiplicity pp collisions, v2 signalsfor prompt charm hadrons are reported for the first time, and are found to be comparable to those forlight-flavor hadron species over a transverse momentum (pT) range of 2–6 GeV. Compared at similarevent multiplicities, the prompt D0 meson v2 values in pp and pPb collisions are similar in magnitude.The v2 values for open beauty hadrons are extracted for the first time via nonprompt D0 mesons inpPb collisions. For pT in the range of 2–5 GeV, the results suggest that v2 for nonprompt D0 mesons issmaller than that for prompt D0 mesons. These new measurements indicate a positive charm hadron v2in pp collisions and suggest a mass dependence in v2 between charm and beauty hadrons in the pPbsystem. These results provide insights into the origin of heavy-flavor quark collectivity in small systems
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2021, The very forward CASTOR calorimeter of the CMS experiment, Journal of Instrumentation, Vol: 16, Pages: 1-65, ISSN: 1748-0221
The physics motivation, detector design, triggers, calibration, alignment, simulation, and overall performance of the very forward CASTOR calorimeter of the CMS experiment are reviewed. The CASTOR Cherenkov sampling calorimeter is located very close to the LHC beam line, at a radial distance of about 1cm from the beam pipe, and at 14.4m from the CMS interaction point, covering the pseudorapidity range of −6.6 < η < −5.2. It was designed to withstand high ambient radiation and strong magnetic fields. The performance of the detector in measurements of forward energy density, jets, and processes characterized by rapidity gaps, is reviewed using data collected in proton and nuclear collisions at the LHC.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for the lepton flavor violating decay tau -> 3 mu in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-37, ISSN: 1029-8479
Results are reported from a search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at s√ = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb−1 recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction ℬ(τ → 3μ) of 8.0 × 10−8 at 90% confidence level is obtained, with an expected upper limit of 6.9 × 10−8.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Evidence for Higgs boson decay to a pair of muons, The Journal of High Energy Physics, Vol: 2021, ISSN: 1029-8479
Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at s√ = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at s√ = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb−1, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is 1.19+0.40−0.39(stat)+0.15−0.14(syst). This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in pPb collisions at root s(NN)=8.16 TeV, Physical Review C: Nuclear Physics, Vol: 103, Pages: 1-17, ISSN: 0556-2813
Event-by-event long-range correlations of azimuthal anisotropy Fourier coefficients (vn) in 8.16 TeV pPb data, collected by the CMS experiment at the CERN Large Hadron Collider, are extracted using a subevent four-particle cumulant technique applied to very low multiplicity events. Each combination of four charged particles is selected from either two, three, or four distinct subevent regions of a pseudorapidity range from −2.4 to 2.4 of the CMS tracker, and with transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant technique, correlations between vn of different orders are measured as functions of particle multiplicity and compared to the standard cumulant method without subevents over a wide event multiplicity range. At high multiplicities, the v2 and v3 coefficients exhibit an anticorrelation; this behavior is observed consistently using various methods. The v2 and v4 correlation strength is found to depend on the number of subevents used in the calculation. As the event multiplicity decreases, the results from different subevent methods diverge because of different contributions of noncollective or few-particle correlations. Correlations extracted with the four-subevent method exhibit a tendency to diminish monotonically toward the lowest multiplicity region (about 20 charged tracks) investigated. These findings extend previous studies to a significantly lower event multiplicity range and establish the evidence for the onset of long-range collective multiparticle correlations in small system collisions.
Sirunyan AM, CMS Collaboration, Tumasyan A, et al., 2021, Search for dark matter produced in association with a leptonically decaying Z boson in proton-proton collisions at s = 13 Te ., European Physical Journal C: Particles and Fields, Vol: 81, Pages: 13-13, ISSN: 1124-1861
A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass energy of 13 Te , collected by the CMS experiment at the LHC in 2016-2018, corresponding to an integrated luminosity of 137 fb - 1 . The search uses the decay channels Z → e e and Z → μ μ . No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Evidence for electroweak production of four charged leptons and two jets in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 812, Pages: 1-25, ISSN: 0370-2693
Evidence is presented for the electroweak (EW) production of two jets (jj) in association with two Zbosons and constraints on anomalous quartic gauge couplings are set. The analysis is based on a data sample of proton-proton collisions at √s=13 TeV collected with the CMS detector in 2016–2018, and corresponding to an integrated luminosity of 137 fb−1. The search is performed in the fully leptonic final state ZZ→ ′ ′, where , ′=e, μ. The EW production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. The cross sections for the EW production are measured in three fiducial volumes and the result is σEW(pp→ZZjj→ ′ ′jj) =0.33+0.11−0.10(stat)+0.04−0.03(syst) fb in the most inclusive volume, in agreement with the standard model prediction of 0.275 ±0.021 fb. Measurements of total cross sections for jj production in association with two Z bosons are also reported. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0, T1, T2, T8, and T9.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for top squark pair production using dilepton final states in pp collision data collected at s√=13TeV, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-30, ISSN: 1124-1861
A search is presented for supersymmetric partners of the top quark (top squarks) in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from bquarks, and missing transverse momentum. The search uses data from proton-proton collisions at s√=13TeV collected with the CMS detector, corresponding to an integrated luminosity of 137fb−1. Hypothetical signal events are efficiently separated from the dominant top quark pair production background with requirements on the significance of the missing transverse momentum and on transverse mass variables. No significant deviation is observed from the expected background. Exclusion limits are set in the context of simplified supersymmetric models with pair-produced lightest top squarks. For top squarks decaying exclusively to a top quark and a lightest neutralino, lower limits are placed at 95% confidence level on the masses of the top squark and the neutralino up to 925 and 450GeV, respectively. If the decay proceeds via an intermediate chargino, the corresponding lower limits on the mass of the lightest top squark are set up to 850GeV for neutralino masses below 420GeV. For top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1.4TeV and 900GeV respectively for the top squark and the lightest neutralino.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at s=13 TeV, Physics Letters B, Vol: 812, Pages: 1-27, ISSN: 0370-2693
The first measurements of production cross sections of polarized same-sign W±W±boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W±scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fb is set on the production cross section for longitudinally polarized same-sign W±W±boson pairs. The electroweak production of same-sign W±W±boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Inclusive search for highly boosted Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at s√ = 13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-49, ISSN: 1029-8479
A search for standard model Higgs bosons (H) produced with transverse momentum (pT) greater than 450 GeV and decaying to bottom quark-antiquark pairs (bb¯¯¯) is performed using proton-proton collision data collected by the CMS experiment at the LHC at s√ = 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb−1. The search is inclusive in the Higgs boson production mode. Highly Lorentz-boosted Higgs bosons decaying to bb¯¯¯ are reconstructed as single large-radius jets, and are identified using jet substructure and a dedicated b tagging technique based on a deep neural network. The method is validated with Z → bb¯¯¯ decays. For a Higgs boson mass of 125 GeV, an excess of events above the background assuming no Higgs boson production is observed with a local significance of 2.5 standard deviations (σ), while the expectation is 0.7. The corresponding signal strength and local significance with respect to the standard model expectation are μH = 3.7 ± 1.2(stat)+0.8−0.7(syst)+0.8−0.5(theo) and 1.9 σ. Additionally, an unfolded differential cross section as a function of Higgs boson pT for the gluon fusion production mode is presented, assuming the other production modes occur at the expected rates.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Dependence of inclusive jet production on the anti-k(T) distance parameter in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-43, ISSN: 1029-8479
The dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter R of the anti-kT algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb−1 collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum pT and rapidity y, for R in the range 0.1 to 1.2 to those using R = 0.4 are presented in the region 84 < pT < 1588 GeV and |y| < 2.0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with R is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of electroweak production of W gamma with two jets in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 811, Pages: 1-27, ISSN: 0370-2693
A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak Wγjj production in a restricted fiducial region is measured as 20.4 ±4.5fband the total cross section for Wγproduction in association with 2 jets in the same fiducial region is 108 ±16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for bottom-type, vectorlike quark pair production in a fully hadronic final state in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 112004 – 1-112004 – 30, ISSN: 1550-2368
A search is described for the production of a pair of bottom-type vectorlike quarks (VLQs), each decaying into a b or ¯b quark and either a Higgs or a Z boson, with a mass greater than 1000 GeV. The analysis is based on data from proton-proton collisions at a 13 TeV center-of-mass energy recorded at the CERN LHC, corresponding to a total integrated luminosity of 137 fb−1. As the predominant decay modes of the Higgs and Z bosons are to a pair of quarks, the analysis focuses on final states consisting of jets resulting from the six quarks produced in the events. Since the two jets produced in the decay of a highly Lorentz-boosted Higgs or Z boson can merge to form a single jet, nine independent analyses are performed, categorized by the number of observed jets and the reconstructed event mode. No signal in excess of the expected background is observed. Lower limits are set on the VLQ mass at 95% confidence level equal to 1570 GeV in the case where the VLQ decays exclusively to a b quark and a Higgs boson, 1390 GeV for when it decays exclusively to a b quark and a Z boson, and 1450 GeV for when it decays equally in these two modes. These limits represent significant improvements over the previously published VLQ limits.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurements of the W boson rapidity, helicity, double-differential cross sections, and charge asymmetry in pp collisions at root s=13 TeV, PHYSICAL REVIEW D, Vol: 102, Pages: 1-50, ISSN: 2470-0010
The differential cross section and charge asymmetry for inclusive W boson production at √s=13 TeV is measured for the two transverse polarization states as a function of the W boson absolute rapidity. The measurement uses events in which a W boson decays to a neutrino and either a muon or an electron. The data sample of proton-proton collisions recorded with the CMS detector at the LHC in 2016 corresponds to an integrated luminosity of 35.9 fb−1. The differential cross section and its value normalized to the total inclusive W boson production cross section are measured over the rapidity range |yW|<2.5. In addition to the total fiducial cross section, the W boson double-differential cross section, d2σ/dpℓTd|ηℓ|, and the charge asymmetry are measured as functions of the charged lepton transverse momentum and pseudorapidity. The precision of these measurements is used to constrain the parton distribution functions of the proton using the next-to-leading order NNPDF3.0 set.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the top quark Yukawa coupling from t(t)over-bar kinematic distributions in the dilepton final state in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-29, ISSN: 1550-2368
A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at √s=13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded with the CMS detector. The coupling strength with respect to the standard model value, Yt, is determined from kinematic distributions in t¯t final states containing ee, μμ, or eμ pairs. Variations of the Yukawa coupling strength lead to modified distributions for t¯t production. In particular, the distributions of the mass of the t¯t system and the rapidity difference of the top quark and antiquark are sensitive to the value of Yt. The measurement yields a best fit value of Yt=1.16+0.24−0.35, bounding Yt<1.54 at a 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Evidence for top quark production in nucleus-nucleus collisions, Physical Review Letters, Vol: 125, Pages: 222001-222001, ISSN: 0031-9007
Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10^{-6} sec, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon center-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production (σ_{tt[over ¯]}) via the selection of charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, σ_{tt[over ¯]}=2.54_{-0.74}^{+0.84} and 2.03_{-0.64}^{+0.71} μb, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of B-c(2S)(+) and B-c*(2S)(+) cross section ratios in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 092007 – 1-092007 – 21, ISSN: 1550-2368
The ratios of the Bc(2S)+ to B+c, B∗c(2S)+ to B+c, and B∗c(2S)+ to Bc(2S)+ production cross sections are measured in proton-proton collisions at √s=13 TeV, using a data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 143 fb−1. The three measurements are made in the B+c meson phase space region defined by the transverse momentum pT>15 GeV and absolute rapidity |y|<2.4, with the excited B(*)c(2S)+ states reconstructed through the B(*)+cπ+π−, followed by the B+c→J/ψπ+ and J/ψ→μ+μ− decays. The Bc(2S)+ to B+c, B∗c(2S)+ to B+c, and B∗c(2S)+ to Bc(2S)+ cross section ratios, including the unknown B(*)c(2S)+→B(*)+cπ+π− branching fractions, are (3.47±0.63(stat)±0.33(syst))%, (4.69±0.71(stat)±0.56(syst))%, and 1.35±0.32(stat)±0.09(syst), respectively. None of these ratios shows a significant dependence on the pT or |y| of the B+c meson. The normalized dipion invariant mass distributions from the decays B(*)c(2S)+→B(*)+cπ+π− are also reported.
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