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1150 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, 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 √<i>s</i> d=13TeV, PHYSICS LETTERS B, Vol: 800, ISSN: 0370-2693
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- Citations: 22
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the single top quark and antiquark production cross sections in the t channel and their ratio in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 800, Pages: 1-30, ISSN: 0370-2693
Measurements of the cross sections for the production of single top quarks and antiquarks in the t channel, and their ratio, are presented for proton-proton collisions at a center-of-mass energy of 13 TeV. The data set used was recorded in 2016 by the CMS detector at the LHC and corresponds to an integrated luminosity of 35.9 fb−1. Events with one muon or electron are selected, and different categories of jet and b jet multiplicity and multivariate discriminators are applied to separate the signal from the background. The cross sections for the t-channel production of single top quarks and antiquarks are measured to be 130±1(stat)±19(syst)pb and 77±1(stat)±12(syst)pb, respectively, and their ratio is 1.68±0.02(stat)±0.05(syst). The results are in agreement with the predictions from the standard model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for electroweak production of a vector-like T quark using fully hadronic final states, The Journal of High Energy Physics, Vol: 36, Pages: 1-64, ISSN: 1029-8479
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 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 → tH and represent the first constraints on T → tZ using hadronic decays of the Z boson with this production mode.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Extraction and validation of a new set of CMS pythia8 tunes from underlying-event measurements, The European Physical Journal C - Particles and Fields, Vol: 80, ISSN: 1124-1861
New sets of CMS underlying-event parameters (“tunes”) are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell–Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of electroweak production of a W boson in association with two jets in proton–proton collisions at s√=13TeV, European Physical Journal C: Particles and Fields, Vol: 80, ISSN: 1124-1861
A measurement is presented of electroweak (EW) production of a W boson in association with two jets in proton–proton collisions at s√=13TeV . The data sample was recorded by the CMS Collaboration at the LHC and corresponds to an integrated luminosity of 35.9 fb−1 . The measurement is performed for the ℓν jj final state (with ℓν indicating a lepton–neutrino pair, and j representing the quarks produced in the hard interaction) in a kinematic region defined by invariant mass mjj>120GeV and transverse momenta pTj>25GeV . The cross section of the process is measured in the electron and muon channels yielding σEW(Wjj)=6.23±0.12(stat)±0.61(syst)pb per channel, in agreement with leading-order standard model predictions. The additional hadronic activity of events in a signal-enriched region is studied, and the measurements are compared with predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. Limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are −2.3<cWWW/Λ2<2.5TeV−2 , −8.8<cW/Λ2<16TeV−2 , and −45<cB/Λ2<46TeV−2 . These results are combined with the CMS EW Zjj analysis, yielding the constraint on the cWWW coupling: −1.8<cWWW/Λ2<2.0TeV−2 .
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Searches for physics beyond the standard model with the MT2 variable in hadronic final states with and without disappearing tracks in proton–proton collisions at s√=13TeV, The European Physical Journal C - Particles and Fields, Vol: 80, ISSN: 1434-6044
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 13TeV, collected by the CMS experiment at the LHC in 2016–2018 and corresponding to an integrated luminosity of 137fb−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 MT2 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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, A Deep Neural Network for Simultaneous Estimation of b Jet Energy and Resolution., Comput Softw Big Sci, Vol: 4
We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton-proton collisions at an energy of s = 13 TeV at the CERN LHC. The algorithm is trained on a large sample of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to b b ¯ .
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for low mass vector resonances decaying into quark-antiquark pairs in proton-proton collisions at root s=13 Tev, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, Pages: 112007-1-112007-24, ISSN: 1550-2368
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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Probing the chiral magnetic wave in pPb and PbPb collisions at root S-NN=5.02 TeV using charge-dependent azimuthal anisotropies, Physical Review C: Nuclear Physics, Vol: 100, Pages: 064908-1-064908-17, ISSN: 0556-2813
Charge-dependent anisotropy Fourier coefficients (vn) of particle azimuthal distributions are measured in pPb and PbPb collisions at √sNN=5.02TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients (v2) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient v3 shows a similar linear dependence with the same slope as seen for v2. The observed similarities between the v2 slopes for pPb and PbPb, as well as the similar slopes for v2 and v3 in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that, at LHC energies, the observed charge asymmetry dependence of v2 in heavy ion collisions arises from a chiral magnetic wave.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Study of the B+ -> J/psi(Lambda)over-barp decay in proton-proton collisions at root s=8 TeV, The Journal of High Energy Physics, Vol: 2019, Pages: 1-38, ISSN: 1029-8479
A study of the B+→J/ψΛ¯¯¯¯p decay using proton-proton collision data collected at 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 B(B+→J/ψΛ¯¯¯¯p)/B(B+→J/ψK∗(892)+) is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011(B))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of Λ¯¯¯¯ and K*(892) + decays to reconstructed final states. The invariant mass distributions of the J/ψΛ¯¯¯¯, J/ψp, and Λ¯¯¯¯p systems produced in the B+→J/ψΛ¯¯¯¯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 observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the Λ¯¯¯¯p system.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for physics beyond the standard model in events with overlapping photons and jets, Physical Review Letters, Vol: 123, Pages: 241801-1-241801-18, ISSN: 0031-9007
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 √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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at root S-NN=5.44 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 799, Pages: 1-23, ISSN: 0370-2693
Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of √sNN=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 |η|<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 |η|<0.5 is found to be , 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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for anomalous triple gauge couplings in WW and WZ production in lepton plus jet events in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2019, Pages: 1-46, ISSN: 1029-8479
A search is presented for three additional operators that would lead to anomalous WWγ 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 eν or μν, 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 < cWWW/Λ2< 1.59 TeV−2, −2.00 < cW/Λ2< 2.65 TeV−2, and −8.78 < cB/Λ2< 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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurements of differential Z boson production cross sections in proton-proton collisions at s√ = 13 TeV, The Journal of High Energy Physics, Vol: 2019, Pages: 1-51, ISSN: 1029-8479
Measurements are presented of the differential cross sections for Z bosons produced in proton-proton collisions at 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 pT, the optimized angular variable ϕ∗η, 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 ϕ∗η< 0.5 and for pZT< 50 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for long-lived particles using delayed photons in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, Pages: 1-24, ISSN: 1550-2368
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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Constraints on anomalous HVV couplings from the production of Higgs bosons decaying to tau lepton pairs, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, Pages: 1-33, ISSN: 1550-2368
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+1.04−0.21)×10−3, fΛ1cos(ϕΛ1)=(0.00+0.53−0.09)×10−3, and fZγΛ1cos(ϕZγΛ1)=(0.0+1.1−1.3)×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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for low-mass quark-antiquark resonances produced in association with a photon at root s=13 TeV, Physical Review Letters, Vol: 123, Pages: 1-17, ISSN: 0031-9007
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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurements of triple-differential cross sections for inclusive isolated-photon+jet events in p p collisions at √s = 8 TeV, Eur Phys J C Part Fields, Vol: 79, ISSN: 1434-6044
Measurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in pp collisions at s√=8 TeV as a function of photon transverse momentum (pγT), photon pseudorapidity (ηγ), and jet pseudorapidity (ηjet). The data correspond to an integrated luminosity of 19.7fb−1 that probe a broad range of the available phase space, for |ηγ|<1.44 and 1.57<|ηγ|<2.50, |ηjet|<2.5, 40<pγT<1000 GeV, and jet transverse momentum, pjetT, > 25GeV. The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for supersymmetry using Higgs boson to diphoton decays at √<i>s</i>=13 TeV, Publisher: SPRINGER
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Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for the production of four top quarks in the single -lepton and opposite -sign dilepton final states in proton -proton collisions at=13 TeV, The Journal of High Energy Physics, Vol: 82, Pages: 1-53, ISSN: 1029-8479
A search for the standard model production of four top quarks (pp → tt¯tt¯) 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 tt¯tt¯ from tt¯ production. No significant deviation is observed from the predicted background. An upper limit is set on the cross section for tt¯tt¯ 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+11−9 fb. The result is also interpreted in the framework of effective field theory.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Combination of CMS searches for heavy resonances decaying to pairs of bosons or leptons, PHYSICS LETTERS B, Vol: 798, Pages: 1-25, ISSN: 0370-2693
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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for anomalous electroweak production of vector boson pairs in association with two jets in proton-proton collisions at 13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 798, Pages: 1-25, ISSN: 0370-2693
A search for anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets in proton-proton collisions at s=13 TeV 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/ 4<2.7,−1.0<fM0/ 4<1.0,and−0.17<fT0/ 4<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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for MSSM Higgs bosons decaying to μ<SUP>+</SUP>μ<SUP>-</SUP> in proton-proton collisions at √<i>s</i>=13TeV, Publisher: ELSEVIER
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Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for new physics in top quark production in dilepton final states in proton-proton collisions at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 79, Pages: 1-29, ISSN: 1124-1861
A search for new physics in top quark production is performed in proton-proton collisions at 13TeV . The data set corresponds to an integrated luminosity of 35.9fb−1 collected in 2016 with the CMS detector. Events with two opposite-sign isolated leptons (electrons or muons), and 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 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 tW from tt¯ events and exploiting the specific sensitivity of the tW process to new physics.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurement of the average very forward energy as a function of the track multiplicity at central pseudorapidities in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: SPRINGER
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- Citations: 11
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for supersymmetry in proton-proton collisions at 13 TeV in final states with jets and missing transverse momentum, Publisher: SPRINGER
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- Citations: 78
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurement of the top quark Yukawa coupling from <i>t</i>(<i>t</i>)over-bar kinematic distributions in the lepton plus jets final state in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: AMER PHYSICAL SOC
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Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for Higgs and Z boson decays to J/psi or Y pairs in the four-muon final state in proton-proton collisions at root s=13 TeV<bold> </bold>, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 797, ISSN: 0370-2693
A search for decays of the Higgs and Z boson to pairs of or (n = 1, 2, 3) mesons, with their subsequent decay to pairs, is presented. The analysis uses data from proton-proton collisions at , collected with the CMS detector at the LHC in 2017 and corresponding to an integrated luminosity of 37.5. 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 pair channel, the limits are and for the Higgs and Z boson, respectively, while in the combined pair channel, the limits are and , 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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at root s(NN)=5.02 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 797, ISSN: 0370-2693
Evidence for the light-by-light scattering process, , in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 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 , pseudorapidity , diphoton invariant mass , diphoton transverse momentum , and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of events for the signal and 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, , is consistent with the standard model prediction. The 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.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for long-lived particles using nonprompt jets and missing transverse momentum with proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 797, Pages: 1-25, ISSN: 0370-2693
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 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.
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