Publications
1150 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of the groomed jet mass in PbPb and pp collisions at root s(NN)=5:02 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
A measurement of the groomed jet mass in PbPb and pp collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with the CMS detector at the LHC is presented. Jet grooming is a recursive procedure which sequentially removes soft constituents of a jet until a pair of hard subjets is found. The resulting groomed jets can be used to study modifications to the parton shower evolution in the presence of the hot and dense medium created in heavy ion collisions. Predictions of groomed jet properties from the pythia and herwig++ event generators agree with the measurements in pp collisions. When comparing the results from the most central PbPb collisions to pp data, a hint of an increase of jets with large jet mass is observed, which could originate from additional medium-induced radiation at a large angle from the jet axis. However, no modification of the groomed mass of the core of the jet is observed for all PbPb centrality classes. The PbPb results are also compared to predictions from the jewel and q-pythia event generators, which predict a large modification of the groomed mass not observed in the data.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Charged-particle nuclear modification factors in XeXe collisions at root S-NN=5.44 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
The differential yields of charged particles having pseudorapidity within |η| < 1 are measured using xenon-xenon (XeXe) collisions at sNN−−−√=5.44 TeV. The data, corresponding to an integrated luminosity of 3.42 μb−1, were collected in 2017 by the CMS experiment at the LHC. The yields are reported as functions of collision centrality and transverse momentum, pT, from 0.5 to 100 GeV. A previously reported pT spectrum from proton-proton collisions at s√=5.02 TeV is used for comparison after correcting for the difference in center-of-mass energy. The nuclear modification factors using this reference, R AA * , are constructed and compared to previous measurements and theoretical predictions. In head-on collisions, the R AA * has a value of 0.17 in the pT range of 6–8 GeV, but increases to approximately 0.7 at 100 GeV. Above ≈6 GeV, the XeXe data show a notably smaller suppression than previous results for lead-lead (PbPb) collisions at sNN−−−√=5.02 TeV when compared at the same centrality (i.e., the same fraction of total cross section). However, the XeXe suppression is slightly greater than that for PbPb in events having a similar number of participating nucleons.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of the production cross section for single top quarks at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
A measurement is presented of the associated production of a single top quark and a W boson in proton-proton collisions at s√=13 TeV by the CMS Collaboration at the CERN LHC. The data collected corresponds to an integrated luminosity of 35.9 fb−1. The measurement is performed using events with one electron and one muon in the final state along with at least one jet originated from a bottom quark. A multivariate discriminant, exploiting the kinematic properties of the events, is used to separate the signal from the dominant tt¯ background. The measured cross section of 63.1 ± 1.8(stat) ± 6.4(syst) ± 2.1 (lumi) pb is in agreement with the standard model expectation.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two bquarks and two tau leptons in proton-proton collisions at root s=13 TeV The CMS Collaboration, PHYSICS LETTERS B, Vol: 785, Pages: 462-488, ISSN: 0370-2693
A search for an exotic decay of the Higgs boson to a pair of light pseudoscalar bosons is performed for the first time in the final state with two b quarks and two τ leptons. The search is motivated in the context of models of physics beyond the standard model (SM), such as two Higgs doublet models extended with a complex scalar singlet (2HDM + S), which include the next-to-minimal supersymmetric SM (NMSSM). The results are based on a data set of proton–proton collisions corresponding to an integrated luminosity of , accumulated by the CMS experiment at the LHC in 2016 at a center-of-mass energy of . Masses of the pseudoscalar boson between 15 and are probed, and no excess of events above the SM expectation is observed. Upper limits between 3 and 12% are set on the branching fraction assuming the SM production of the Higgs boson. Upper limits are also set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different 2HDM + S scenarios. Assuming the SM production cross section for the Higgs boson, the upper limit on this quantity is as low as 20% for a mass of the pseudoscalar of in the NMSSM.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Study of jet quenching with isolated-photon plus jet correlations in PbPb and pp collisions at root s(NN)=5.02 TeV, PHYSICS LETTERS B, Vol: 785, Pages: 14-39, ISSN: 0370-2693
Measurements of azimuthal angle and transverse momentum ( ) correlations of isolated photons and associated jets are reported for and PbPb collisions at . The data were recorded with the CMS detector at the CERN LHC. For events containing a leading isolated photon with and an associated jet with , the photon+jet azimuthal correlation and imbalance in PbPb collisions are studied as functions of collision centrality and . The results are compared to reference data collected at the same collision energy and to predictions from several theoretical models for parton energy loss. No evidence of broadening of the photon+jet azimuthal correlations is observed, while the ratio decreases significantly for PbPb data relative to the reference. All models considered agree within uncertainties with the data. The number of associated jets per photon with is observed to be shifted towards lower values in central PbPb collisions compared to collisions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Pseudorapidity and transverse momentum dependence of flow harmonics in pPb and PbPb collisions, PHYSICAL REVIEW C, Vol: 98, ISSN: 2469-9985
Measurements of azimuthal angular correlations are presented for high-multiplicity pPb collisions at √sNN=5.02TeV and peripheral PbPb collisions at √sNN=2.76TeV. The data used in this work were collected with the Compact Muon Solenoid (CMS) detector at the European Organization for Nuclear Research (CERN) Large Hadron Collider (LHC). Fourier coefficients as functions of transverse momentum and pseudorapidity are studied using the scalar product method; four-, six-, and eight-particle cumulants; and the Lee-Yang zero technique. The influence of event plane decorrelation is evaluated using the scalar product method and found to account for most of the observed pseudorapidity dependence.
Sirunyan AM, Sirunyan AM, Tumasyan A, et al., 2018, Search for Pair-Produced Resonances Each Decaying into at Least Four Quarks in Proton-Proton Collisions at root s=13 TeV, PHYSICAL REVIEW LETTERS, Vol: 121, ISSN: 0031-9007
This Letter presents the results of a search for pair-produced particles of masses above 100 GeV that each decay into at least four quarks. Using data collected by the CMS experiment at the LHC in 2015–2016, corresponding to an integrated luminosity of 38.2 fb−1, reconstructed particles are clustered into two large jets of similar mass, each consistent with four-parton substructure. No statistically significant excess of data over the background prediction is observed in the distribution of average jet mass. Pair-produced squarks with dominant hadronic R-parity-violating decays into four quarks and with masses between 0.10 and 0.72 TeV are excluded at 95% confidence level. Similarly, pair-produced gluinos that decay into five quarks are also excluded with masses between 0.10 and 1.41 TeV at 95% confidence level. These are the first constraints that have been placed on pair-produced particles with masses below 400 GeV that decay into four or five quarks, bridging a significant gap in the coverage of R-parity-violating supersymmetry parameter space.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Observation of the Z -> psi l(+)l(-) Decay in pp Collisions at root s=13 TeV, Physical Review Letters, Vol: 121, ISSN: 0031-9007
This Letter presents the observation of the rare Z boson decay Z→ψℓ+ℓ−. Here, ψ represents contributions from direct J/ψ and ψ(2S)→J/ψX, ℓ+ℓ− is a pair of electrons or muons, and the J/ψ meson is detected via its decay to μ+μ−. The sample of proton-proton collision data, collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponds to an integrated luminosity of 35.9 fb−1. The signal is observed with a significance in excess of 5 standard deviations. After subtraction of the ψ(2S)→J/ψX contribution, the ratio of the branching fraction of the exclusive decay Z→J/ψℓ+ℓ− to the decay Z→μ+μ−μ+μ− within a fiducial phase space is measured to be B(Z→J/ψℓ+ℓ−)/B(Z→μ+μ−μ+μ−)=0.67±0.18(stat)±0.05(syst).
Akchurin N, Apreysan A, Banerjee S, et al., 2018, First beam tests of prototype silicon modules for the CMS High Granularity Endcap Calorimeter, JOURNAL OF INSTRUMENTATION, Vol: 13, ISSN: 1748-0221
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Performance of reconstruction and identification of tau leptons decaying to hadrons and nu(tau) in pp collisions at root s=13 TeV, Journal of Instrumentation, Vol: 13, ISSN: 1748-0221
The algorithm developed by the CMS Collaboration to reconstruct and identify τ leptons produced in proton-proton collisions at √s=7 and 8 TeV, via their decays to hadrons and a neutrino, has been significantly improved. The changes include a revised reconstruction of π0 candidates, and improvements in multivariate discriminants to separate τ leptons from jets and electrons. The algorithm is extended to reconstruct τ leptons in highly Lorentz-boosted pair production, and in the high-level trigger. The performance of the algorithm is studied using proton-proton collisions recorded during 2016 at √s=13 TeV, corresponding to an integrated luminosity of 35.9 fb-1. The performance is evaluated in terms of the efficiency for a genuine τ lepton to pass the identification criteria and of the probabilities for jets, electrons, and muons to be misidentified as τ leptons. The results are found to be very close to those expected from Monte Carlo simulation.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for new physics in dijet angular distributions using proton-proton collisions at root s=13 TeV and constraints on dark matter and other models, EUROPEAN PHYSICAL JOURNAL C, Vol: 78, ISSN: 1434-6044
A search is presented for physics beyond the standard model, based on measurements of dijet angular distributions in proton–proton collisions at √=13TeV. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 35.9fb−1. The observed distributions, corrected to particle level, are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Constraints are placed on models containing quark contact interactions, extra spatial dimensions, quantum black holes, or dark matter, using the detector-level distributions. In a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 or 17.5TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani–Hamed–Dimopoulos–Dvali model of extra dimensions. In the Giudice–Rattazzi–Wells convention, the cutoff scale is excluded up to 10.1TeV. The production of quantum black holes is excluded for masses below 5.9 and 8.2TeV, depending on the model. For the first time, lower limits between 2.0 and 4.6TeVare set on the mass of a dark matter mediator for (axial-)vector mediators, for the universal quark coupling q=1.0.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for Z gamma resonances using leptonic and hadronic final states in proton-proton collisions at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
A search is presented for resonances decaying to a Z boson and a photon. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, and collected with the CMS detector at the LHC in 2016. Two decay modes of the Z boson are investigated. In the leptonic channels, the Z boson candidates are reconstructed using electron or muon pairs. In the hadronic channels, they are identified using a large-radius jet, containing either light-quark or b quark decay products of the Z boson, via jet substructure and advanced b quark tagging techniques. The results from these channels are combined and interpreted in terms of upper limits on the product of the production cross section and the branching fraction to Zγ for narrow and broad spin-0 resonances with masses between 0.35 and 4.0 TeV, providing thereby the most stringent limits on such resonances.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for a heavy resonance decaying into a Z boson and a Z or W boson in 2l2q final states at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search has been performed for heavy resonances decaying to ZZ or ZW in 2ℓ2q final states, with two charged leptons (ℓ = e, μ) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of s√=13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W′ bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Observation of Higgs Boson decay to bottom quarks, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The observation of the standard model (SM) Higgs boson decay to a pair of bottom quarks is presented. The main contribution to this result is from processes in which Higgs bosons are produced in association with a W or Z boson (VH), and are searched for in final states including 0, 1, or 2 charged leptons and two identified bottom quark jets. The results from the measurement of these processes in a data sample recorded by the CMS experiment in 2017, comprising 41.3 fb−1 of proton-proton collisions at √s=13 TeV, are described. When combined with previous VH measurements using data collected at √s=7, 8, and 13 TeV, an excess of events is observed at mH=125 GeV with a significance of 4.8 standard deviations, where the expectation for the SM Higgs boson is 4.9. The corresponding measured signal strength is 1.01±0.22. The combination of this result with searches by the CMS experiment for H→b¯b in other production processes yields an observed (expected) significance of 5.6 (5.5) standard deviations and a signal strength of 1.04±0.20.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for top squarks decaying via four-body or chargino-mediated modes in single-lepton final states in proton-proton collisions at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
A search for the pair production of the lightest supersymmetric partner of the top quark (t~1) is presented. The search focuses on a compressed scenario where the mass difference between the top squark and the lightest supersymmetric particle, often considered to be the lightest neutralino (χ~01), is smaller than the mass of the W boson. The proton-proton collision data were recorded by the CMS experiment at a centre-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb−1. In this search, two decay modes of the top squark are considered: a four-body decay into a bottom quark, two additional fermions, and a χ~01; and a decay via an intermediate chargino. Events are selected using the presence of a high-momentum jet, significant missing transverse momentum, and a low transverse momentum electron or muon. Two analysis techniques are used, targeting different decay modes of the t~1: a sequential selection and a multivariate technique. No evidence for the production of top squarks is found, and mass limits at 95% confidence level are set that reach up to 560 GeV, depending on the m(t~1)−m(χ~01) mass difference and the decay mode.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for dark matter produced in association with a Higgs boson decaying to gamma gamma or tau(+)tau(-) at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
A search for dark matter particles is performed by looking for events with large transverse momentum imbalance and a recoiling Higgs boson decaying to either a pair of photons or a pair of τ leptons. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected at the CERN LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb−1. No significant excess over the expected standard model background is observed. Upper limits at 95% confidence level are presented for the product of the production cross section and branching fraction in the context of two benchmark simplified models. For the Z′-two-Higgs-doublet model (where Z′ is a new massive boson mediator) with an intermediate heavy pseudoscalar particle of mass mA = 300 GeV and mDM = 100 GeV, the Z′ masses from 550 GeV to 1265 GeV are excluded. For a baryonic Z′ model, with mDM = 1 GeV, Z′ masses up to 615 GeV are excluded. Results are also presented for the spin-independent cross section for the dark matter-nucleon interaction as a function of the mass of the dark matter particle. This is the first search for dark matter particles produced in association with a Higgs boson decaying to two τ leptons.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for third-generation scalar leptoquarks decaying to a top quark and a tau lepton at root s=13 TeV, EUROPEAN PHYSICAL JOURNAL C, Vol: 78, ISSN: 1434-6044
A search for pair production of heavy scalar leptoquarks (LQs), each decaying into a top quark and a τ lepton, is presented. The search considers final states with an electron or a muon, one or two τ leptons that decayed to hadrons, and additional jets. The data were collected in 2016 in proton–proton collisions at s√=13TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9fb−1. No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay LQ→tτ, upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900GeV at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a τ lepton.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of the Z/gamma* -> tau tau cross section in pp collisions at root s=13 TeV and validation of tau lepton analysis techniques, EUROPEAN PHYSICAL JOURNAL C, Vol: 78, ISSN: 1434-6044
A measurement is presented of the Z/γ∗→ττ cross section in pp collisions at s√=13 TeV, using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 2.3 fb−1. The product of the inclusive cross section and branching fraction is measured to be σ(pp→Z/γ∗+X)B(Z/γ∗→ττ)=1848±12(stat)±67 (syst \,+\,lumi) pb, in agreement with the standard model expectation, computed at next-to-next-to-leading order accuracy in perturbative quantum chromodynamics. The measurement is used to validate new analysis techniques relevant for future measurements of τ lepton production. The measurement also provides the reconstruction efficiency and energy scale for τ decays to hadrons+ντ final states, determined with respective relative uncertainties of 2.2 and 0.9%.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for additional neutral MSSM Higgs bosons in the tau tau final state in proton-proton collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search is presented for additional neutral Higgs bosons in the τ τ final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the m h hod + scenario these limits translate into a 95% CL exclusion of tan β > 6 for neutral Higgs boson masses below 250 GeV, where tan β is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tan β = 60.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of the weak mixing angle using the forward-backward asymmetry of Drell-Yan events in pp collisions at 8 TeV, EUROPEAN PHYSICAL JOURNAL C, Vol: 78, ISSN: 1434-6044
A measurement is presented of the effective leptonic weak mixing angle (sin2θℓeff) using the forward–backward asymmetry of Drell–Yan lepton pairs (μμ and e e) produced in proton–proton collisions at s√=8TeV at the CMS experiment of the LHC. The data correspond to integrated luminosities of 18.8 and 19.6fb−1 in the dimuon and dielectron channels, respectively, containing 8.2 million dimuon and 4.9 million dielectron events. With more events and new analysis techniques, including constraints obtained on the parton distribution functions from the measured forward–backward asymmetry, the statistical and systematic uncertainties are significantly reduced relative to previous CMS measurements. The extracted value of sin2θℓeff from the combined dilepton data is sin2θℓeff=0.23101±0.00036(stat)±0.00018(syst)±0.00016(theo)±0.00031(parton distributions in proton)=0.23101±0.00053.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Observation of the chi(b1)(3P) and chi(b2)(3P) and measurement of their masses, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The χb1(3P) and χb2(3P) states are observed through their Υ(3S)γ decays, using an event sample of proton-proton collisions collected by the CMS experiment at the CERN LHC. The data were collected at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 80.0 fb−1. The Υ(3S) mesons are identified through their dimuon decay channel, while the low-energy photons are detected after converting to e+e− pairs in the silicon tracker, leading to a χb(3P) mass resolution of 2.2 MeV. This is the first time that the J=1 and 2 states are well resolved and their masses individually measured: 10513.42±0.41(stat)±0.18(syst) MeV and 10524.02±0.57(stat)±0.18(syst) MeV; they are determined with respect to the world-average value of the Υ(3S) mass, which has an uncertainty of 0.5 MeV. The mass splitting is measured to be 10.60±0.64(stat)±0.17(syst) MeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of charged particle spectra in minimum-bias events from proton-proton collisions at root s =13 TeV, European Physical Journal C, Vol: 78, ISSN: 1434-6044
Pseudorapidity, transverse momentum, and multiplicity distributions are measured in the pseudorapidity range |η|<2.4 for charged particles with transverse momenta satisfying pT>0.5GeV in proton–proton collisions at a center-of-mass energy of s√=13TeV. Measurements are presented in three different event categories. The most inclusive of the categories corresponds to an inelastic p p data set, while the other two categories are exclusive subsets of the inelastic sample that are either enhanced or depleted in single diffractive dissociation events. The measurements are compared to predictions from Monte Carlo event generators used to describe high-energy hadronic interactions in collider and cosmic-ray physics.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for vector-like T and B quark pairs in final states with leptons at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search is presented for pair production of heavy vector-like T and B quarks in proton-proton collisions at s√=13 TeV. The data sample corresponds to an integrated luminosity of 35.9 fb−1, collected with the CMS detector at the CERN LHC in 2016. Pair production of T quarks would result in a wide range of final states, since vector-like T quarks of charge 2e/3 are predicted to decay to bW, tZ, and tH. Likewise, vector-like B quarks are predicted to decay to tW, bZ, and bH. Three channels are considered, corresponding to final states with a single lepton, two leptons with the same sign of the electric charge, or at least three leptons. The results exclude T quarks with masses below 1140–1300 GeV and B quarks with masses below 910–1240 GeV for various branching fraction combinations, extending the reach of previous CMS searches by 200–600 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for resonant pair production of Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at 13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for a narrow-width resonance decaying into two Higgs bosons, each decaying into a bottom quark-antiquark pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 35.9 fb−1 at s√=13 TeV recorded by the CMS detector at the LHC. No evidence for such a signal is observed. Upper limits are set on the product of the production cross section for the resonance and the branching fraction for the selected decay mode in the resonance mass range from 260 to 1200 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Elliptic Flow of Charm and Strange Hadrons in High-Multiplicity p plus Pb Collisions at root(NN)-N-s=8.16 TeV, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The elliptic azimuthal anisotropy coefficient (v2) is measured for charm (D0) and strange (K0S, Λ, Ξ−, and Ω−) hadrons, using a data sample of p+Pb collisions collected by the CMS experiment, at a nucleon-nucleon center-of-mass energy of √sNN=8.16 TeV. A significant positive v2 signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity p+Pb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller v2 than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at √sNN=5.02 TeV, also presented.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for beyond the standard model Higgs bosons decaying into a b(b)over-bar pair in pp collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for Higgs bosons that decay into a bottom quark-antiquark pair and are accompanied by at least one additional bottom quark is performed with the CMS detector. The data analyzed were recorded in proton-proton collisions at a centre-of-mass energy of s√=13 TeV at the LHC, corresponding to an integrated luminosity of 35.7 fb−1. The final state considered in this analysis is particularly sensitive to signatures of a Higgs sector beyond the standard model, as predicted in the generic class of two Higgs doublet models (2HDMs). No signal above the standard model background expectation is observed. Stringent upper limits on the cross section times branching fraction are set for Higgs bosons with masses up to 1300 GeV. The results are interpreted within several MSSM and 2HDM scenarios.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Evidence for associated production of a Higgs boson with a top quark pair in final states with electrons, muons, and hadronically decaying tau leptons at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2018, ISSN: 1029-8479
Results of a search for the standard model Higgs boson produced in association with a top quark pair (tt¯H) in final states with electrons, muons, and hadronically decaying τ leptons are presented. The analyzed data set corresponds to an integrated luminosity of 35.9 fb−1 recorded in proton-proton collisions at s√=13 TeV by the CMS experiment in 2016. The sensitivity of the search is improved by using matrix element and machine learning methods to separate the signal from backgrounds. The measured signal rate amounts to 1.23 − 0.43 + 0.45 times the production rate expected in the standard model, with an observed (expected) significance of 3.2σ (2.8σ), which represents evidence for tt¯H production in those final states. An upper limit on the signal rate of 2.1 times the standard model production rate is set at 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Constraints on models of scalar and vector leptoquarks decaying to a quark and a neutrino at root s=13 TeV, PHYSICAL REVIEW D, Vol: 98, ISSN: 2470-0010
The results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the MT2 variable. The analysis uses proton-proton collision data at √s=13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb−1. Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to tν, and 50% to bτ, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to tν, LQ masses below 1530 GeV are excluded assuming the Yang-Mills case with coupling κ=1, or 1115 GeV in the minimal coupling case κ=0, placing the most stringent constraint to date from pair production of vector LQs.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for R-parity violating supersymmetry in pp collisions at root s=13 TeV using bjets in a final state with a single lepton, many jets, and high sum of large-radius jet masses, Physics Letters B, Vol: 783, Pages: 114-139, ISSN: 0370-2693
Results are reported from a search for physics beyond the standard model in proton–proton collisions at a center-of-mass energy of . The search uses a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event. The data sample corresponds to an integrated luminosity of 35.9 fb−1 recorded by the CMS experiment at the LHC. No significant excess beyond the prediction from standard model processes is observed. The results are interpreted in terms of upper limits on the production cross section for R-parity violating supersymmetric extensions of the standard model using a benchmark model of gluino pair production, in which each gluino decays promptly via . Gluinos with a mass below 1610 GeV are excluded at 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Constraining Gluon Distributions in Nuclei Using Dijets in Proton-Proton and Proton-Lead Collisions at root s(NN)=5.02 TeV, PHYSICAL REVIEW LETTERS, Vol: 121, ISSN: 0031-9007
The pseudorapidity distributions of dijets as functions of their average transverse momentum (paveT) are measured in proton-lead (pPb) and proton-proton (pp) collisions. The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the pPb spectra with respect to the pp spectra is observed in all paveT intervals investigated. The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken x in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.
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