Publications
1150 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of properties of B(s)(0)s -> mu(+)mu(-) decays and search for B-0 -> mu(+)mu(-) with the CMS experiment, The Journal of High Energy Physics, Vol: 2020, Pages: 1-49, ISSN: 1029-8479
Results are reported for the B0s→ μ+μ− branching fraction and effective lifetime and from a search for the decay B0→ μ+μ−. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7 TeV (5 fb−1), 8 TeV (20 fb−1), and 13 TeV (36 fb−1). The branching fractions are determined by measuring event yields relative to B+→ J/ψK+ decays (with J/ψ → μ+μ−), which results in the reduction of many of the systematic uncertainties. The decay B0s→ μ+μ− is observed with a significance of 5.6 standard deviations. The branching fraction is measured to be B(B0s→μ+μ−)=[2.9±0.7(exp)±0.2(frag)]×10−9, where the first uncertainty combines the experimental statistical and systematic contributions, and the second is due to the uncertainty in the ratio of the B0s and the B+ fragmentation functions. No significant excess is observed for the decay B0→ μ+μ−, and an upper limit of ℬ(B0 → μ+μ−) < 3.6 × 10−10 is obtained at 95% confidence level. The B0s→ μ+μ− effective lifetime is measured to be τμ+μ−=1.70+0.61−0.44 ps. These results are consistent with standard model predictions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for heavy Higgs bosons decaying to a top quark pair in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: SPRINGER
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- Citations: 16
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Constraints on the χc1 versus χc2 polarizations in proton-proton collisions at √s=8 TeV, Physical Review Letters, Vol: 124, ISSN: 0031-9007
The polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e−, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ− decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Experimental study of different silicon sensor options for the upgrade of the CMS Outer Tracker, Journal of Instrumentation, Vol: 15, Pages: 1-34, ISSN: 1748-0221
During the high-luminosity phase of the LHC (HL-LHC), planned to start in 2027, the accelerator is expected to deliver an instantaneous peak luminosity of up to 7.5×1034 cm−2 s−1. A total integrated luminosity of 0300 or even 0400 fb−1 is foreseen to be delivered to the general purpose detectors ATLAS and CMS over a decade, thereby increasing the discovery potential of the LHC experiments significantly. The CMS detector will undergo a major upgrade for the HL-LHC, with entirely new tracking detectors consisting of an Outer Tracker and Inner Tracker. However, the new tracking system will be exposed to a significantly higher radiation than the current tracker, requiring new radiation-hard sensors. CMS initiated an extensive irradiation and measurement campaign starting in 2009 to systematically compare the properties of different silicon materials and design choices for the Outer Tracker sensors. Several test structures and sensors were designed and implemented on 18 different combinations of wafer materials, thicknesses, and production technologies. The devices were electrically characterized before and after irradiation with neutrons, and with protons of different energies, with fluences corresponding to those expected at different radii of the CMS Outer Tracker after 0300 fb−1. The tests performed include studies with β sources, lasers, and beam scans. This paper compares the performance of different options for the HL-LHC silicon sensors with a focus on silicon bulk material and thickness.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Production of Lambda(+)(c) baryons in proton-proton and lead-lead collisions at root S-NN=5.02 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 803, Pages: 1-23, ISSN: 0370-2693
The transverse momentum (pT) spectra of inclusively produced +cbaryons are measured via the exclusive decay channel +c→pK−π+using the CMS detector at the LHC. Spectra are measured as a function of transverse momentum in proton-proton (pp) and lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measurement is performed within the +crapidity interval |y| <1in the pTrange of 5–20 GeV/cin pp and 10–20 GeV/cin PbPb collisions. The observed yields of +cfor pTof 10–20 GeV/csuggest a suppression in central PbPb collisions compared to ppcollisions scaled by the number of nucleon-nucleon (NN) interactions. The +c/D0production ratio in pp collisions is compared to theoretical models. In PbPb collisions, this ratio is consistent with the result from pp collisions in their common pTrange.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Running of the top quark mass from proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 803, Pages: 1-24, ISSN: 0370-2693
The running of the top quark mass is experimentally investigated for the first time. The mass of the top quark in the modified minimal subtraction () renormalization scheme is extracted from a comparison of the differential top quark-antiquark () cross section as a function of the invariant mass of the system to next-to-leading-order theoretical predictions. The differential cross section is determined at the parton level by means of a maximum-likelihood fit to distributions of final-state observables. The analysis is performed using candidate events in the e± μ∓ channel in proton-proton collision data at a centre-of-mass energy of 13 TeV recorded by the CMS detector at the CERN LHC in 2016, corresponding to an integrated luminosity of 35.9. The extracted running is found to be compatible with the scale dependence predicted by the corresponding renormalization group equation. In this analysis, the running is probed up to a scale of the order of 1 TeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Study of excited Lambda(0)(b) states decaying to Lambda(0)(b)pi(+)pi(-) in proton-proton collisions at root s=13TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 803, Pages: 1-22, ISSN: 0370-2693
A study of excited Λ0bbaryons is reported, based on a data sample collected in 2016–2018 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 up to 140 fb−1. The existence of four excited Λ0bstates: Λ0b(5912)0, Λ0b(5920)0, Λ0b(6146)0, and Λ0b(6152)0in the Λ0bπ+π−mass spectrum is confirmed, and their masses are measured. The Λ0bπ+π−mass distribution exhibits a broad excess of events in the region of 6040–6100 MeV, whose origin cannot be discerned with the present data.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the t(t)over-barb(b)over-bar production cross section in the all-jet final state in pp collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 803, Pages: 1-26, ISSN: 0370-2693
A measurement of the production cross section of top quark pairs in association with two bjets (ttbb) is presented using data collected in proton-proton collisions at √s=13 TeV by the CMS detector at the LHC corresponding to an integrated luminosity of 35.9fb−1. The cross section is measured in the all-jet decay channel of the top quark pair by selecting events containing at least eight jets, of which at least two are identified as originating from the hadronization of bquarks. A combination of multivariate analysis techniques is used to reduce the large background from multijet events not containing a top quark pair, and to help discriminate between jets originating from top quark decays and other additional jets. The cross section is determined for the total phase space to be 5.5 ±0.3 (stat)+1.6−1.3(syst) pb and also measured for two fiducial ttbb definitions. The measured cross sections are found to be larger than theoretical predictions by a factor of 1.5–2.4, corresponding to 1–2 standard deviations.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for a narrow resonance lighter than 200 GeV decaying to a pair of muons in proton-proton collisions at sqrt[s]=13 TeV., Physical Review Letters`, Vol: 124, Pages: 131802-1-131802-17, ISSN: 0031-9007
A search is presented for a narrow resonance decaying to a pair of oppositely charged muons using sqrt[s]=13 TeV proton-proton collision data recorded at the LHC. In the 45-75 and 110-200 GeV resonance mass ranges, the search is based on conventional triggering and event reconstruction techniques. In the 11.5-45 GeV mass range, the search uses data collected with dimuon triggers with low transverse momentum thresholds, recorded at high rate by storing a reduced amount of trigger-level information. The data correspond to integrated luminosities of 137 and 96.6 fb^{-1} for conventional and high-rate triggering, respectively. No significant resonant peaks are observed in the probed mass ranges. The search sets the most stringent constraints to date on a dark photon in the ∼30-75 and 110-200 GeV mass ranges.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for supersymmetry in pp collisions at root s=13 TeV with 137 fb(-1) in final states with a single lepton using the sum of masses of large-radius jets, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 052010-1-052010-33, ISSN: 1550-2368
Results are reported from a search for new physics beyond the standard model in proton-proton collisions in final states with a single lepton; multiple jets, including at least one jet tagged as originating from the hadronization of a bottom quark; and large missing transverse momentum. The search uses a sample of proton-proton collision data at √s=13 TeV, corresponding to 137 fb−1, recorded by the CMS experiment at the LHC. The signal region is divided into categories characterized by the total number of jets, the number of bottom quark jets, the missing transverse momentum, and the sum of masses of large-radius jets. The observed event yields in the signal regions are consistent with estimates of standard model backgrounds based on event yields in the control regions. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production in which each gluino decays into a top quark-antiquark pair and a stable, unobserved neutralino, which generates missing transverse momentum in the event. Scenarios with gluino masses up to about 2150 GeV are excluded at 95% confidence level (or more) for neutralino masses up to 700 GeV. The highest excluded neutralino mass is about 1250 GeV, which holds for gluino masses around 1850 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, A search for the standard model Higgs boson decaying to charm quarks, The Journal of High Energy Physics, Vol: 2020, Pages: 1-54, ISSN: 1029-8479
A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W → ℓν, Z → ℓℓ, and Z → νν, where ℓ is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section σ(VH)B(H→cc¯¯) of 4.5 (2.4+1.0−0.7) pb, corresponding to 70 (37) times the standard model prediction.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, A multi-dimensional search for new heavy resonances decaying to boosted WW , WZ , or ZZ boson pairs in the dijet final state at 13 Te, European Physical Journal C: Particles and Fields, Vol: 80, ISSN: 1124-1861
A search in an all-jet final state for new massive resonances decaying to W W , W Z , or Z Z boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb−1 recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13 TeV. The search is focussed on potential narrow-width resonances with masses above 1.2 TeV, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1 Z′ and W′ resonances with masses below 3.5 and 3.8 TeV, respectively, are excluded at 95% confidence level. In a bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2 TeV, respectively. The limits presented in this paper are the best to date in the dijet final state.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for a heavy pseudoscalar Higgs boson decaying into a 125 GeV Higgs boson and a Z boson in final states with two tau and two light leptons at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-46, ISSN: 1029-8479
A search is performed for a pseudoscalar Higgs boson, A, decaying into a 125 GeV Higgs boson h and a Z boson. The h boson is specifically targeted in its decay into a pair of tau leptons, while the Z boson decays into a pair of electrons or muons. A data sample of proton-proton collisions collected by the CMS experiment at the LHC at s√ = 13 TeV is used, corresponding to an integrated luminosity of 35.9 fb−1. No excess above the standard model background expectations is observed in data. A model-independent upper limit is set on the product of the gluon fusion production cross section for the A boson and the branching fraction to Zh → ℓℓττ. The observed upper limit at 95% confidence level ranges from 27 to 5 fb for A boson masses from 220 to 400 GeV, respectively. The results are used to constrain the extended Higgs sector parameters for two benchmark scenarios of the minimal supersymmetric standard model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for physics beyond the standard model in multilepton final states in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-50, ISSN: 1029-8479
A search for physics beyond the standard model in events with at least three charged leptons (electrons or muons) is presented. The data sample corresponds to an integrated luminosity of 137 fb−1 of proton-proton collisions at s√ = 13 TeV, collected with the CMS detector at the LHC in 2016–2018. The two targeted signal processes are pair production of type-III seesaw heavy fermions and production of a light scalar or pseudoscalar boson in association with a pair of top quarks. The heavy fermions may be manifested as an excess of events with large values of leptonic transverse momenta or missing transverse momentum. The light scalars or pseudoscalars may create a localized excess in the dilepton mass spectra. The results exclude heavy fermions of the type-III seesaw model for masses below 880 GeV at 95% confidence level in the scenario of equal branching fractions to each lepton flavor. This is the most restrictive limit on the flavor-democratic scenario of the type-III seesaw model to date. Assuming a Yukawa coupling of unit strength to top quarks, branching fractions of new scalar (pseudoscalar) bosons to dielectrons or dimuons above 0.004 (0.03) and 0.04 (0.03) are excluded at 95% confidence level for masses in the range 15–75 and 108–340 GeV, respectively. These are the first limits in these channels on an extension of the standard model with scalar or pseudoscalar particles.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of top quark pair production in association with a Z boson in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-50, ISSN: 1029-8479
A measurement of the inclusive cross section of top quark pair production in association with a Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC is performed. The data sample corresponds to an integrated luminosity of 77.5 fb−1, collected by the CMS experiment during 2016 and 2017. The measurement is performed using final states containing three or four charged leptons (electrons or muons), and the Z boson is detected through its decay to an oppositely charged lepton pair. The production cross section is measured to be σ(tt¯Z) = 0.95 ± 0.05 (stat) ± 0.06 (syst) pb. For the first time, differential cross sections are measured as functions of the transverse momentum of the Z boson and the angular distribution of the negatively charged lepton from the Z boson decay. The most stringent direct limits to date on the anomalous couplings of the top quark to the Z boson are presented, including constraints on the Wilson coefficients in the framework of the standard model effective field theory.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for new neutral Higgs bosons through the H -> ZA -><mml:msup>l+</mml:msup><mml:msup>l-</mml:msup>bb<mml:mo stretchy="true"><overbar></mml:mover> process in pp collisions at <mml:msqrt>s</mml:msqrt>=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-40, ISSN: 1029-8479
This paper reports on a search for an extension to the scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy s√ = 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb−1. Data and predictions from the standard model are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of the Lambda(0)(b) -> J/psi Lambda phi decay in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 802, Pages: 1-23, ISSN: 0370-2693
The observation of the 0b→J/ψ φdecay is reported using proton-proton collision data collected at √s=13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60 fb−1. The ratio of the branching fractions B( 0b→J/ψ φ)/B( 0b→ψ(2S) )is measured to be (8.26 ±0.90 (stat)±0.68 (syst)±0.11(B)) ×10−2, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of φand ψ(2S)decays to the reconstructed final states.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for a heavy Higgs boson decaying to a pair of W bosons in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-54, ISSN: 1029-8479
A search for a heavy Higgs boson in the mass range from 0.2 to 3.0 TeV, decaying to a pair of W bosons, is presented. The analysis is based on proton-proton collisions at s√ = 13 TeV recorded by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb−1. The W boson pair decays are reconstructed in the 2ℓ2ν and ℓν2q final states (with ℓ = e or μ). Both gluon fusion and vector boson fusion production of the signal are considered. Interference effects between the signal and background are also taken into account. The observed data are consistent with the standard model (SM) expectation. Combined upper limits at 95% confidence level on the product of the cross section and branching fraction exclude a heavy Higgs boson with SM-like couplings and decays up to 1870 GeV. Exclusion limits are also set in the context of a number of two-Higgs-doublet model formulations, further reducing the allowed parameter space for SM extensions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for dark matter particles produced in association with a Higgs boson in proton-proton collisions at √s=13TeV, Publisher: SPRINGER
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Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Bose-Einstein correlations of charged hadrons in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-52, ISSN: 1029-8479
Bose-Einstein correlations of charged hadrons are measured over a broad multiplicity range, from a few particles up to about 250 reconstructed charged hadrons in proton-proton collisions at s√ = 13 TeV. The results are based on data collected using the CMS detector at the LHC during runs with a special low-pileup configuration. Three analysis techniques with different degrees of dependence on simulations are used to remove the non-Bose-Einstein background from the correlation functions. All three methods give consistent results. The measured lengths of homogeneity are studied as functions of particle multiplicity as well as average pair transverse momentum and mass. The results are compared with data from both CMS and ATLAS at s√ = 7 TeV, as well as with theoretical predictions.
CMS Collaboration, Sirunyan AM, Tumasyan A, et al., 2020, Search for direct pair production of supersymmetric partners to the τ lepton in proton-proton collisions at √s = 13 TeV, The European Physical Journal C - Particles and Fields, Vol: 80, ISSN: 1124-1861
A search is presented for τ slepton pairs produced in proton–proton collisions at a center-of-mass energy of 13TeV. The search is carried out in events containing two τ leptons in the final state, on the assumption that each τ slepton decays primarily to a τ lepton and a neutralino. Events are considered in which each τ lepton decays to one or more hadrons and a neutrino, or in which one of the τ leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2fb−1. The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for τ slepton pair production in various models for τ slepton masses between 90 and 200GeV and neutralino masses of 1, 10, and 20GeV. In the case of purely left-handed τ slepton production and decay to a τ lepton and a neutralino with a mass of 1GeV, the strongest limit is obtained for a τ slepton mass of 125GeV at a factor of 1.14 larger than the theoretical cross section.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the top quark pair production cross section in dilepton final states containing one tau lepton in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-41, ISSN: 1029-8479
he cross section of top quark pair production is measured in the tt¯→(ℓνℓ)(τhντ)bb¯¯¯ final state, where τh refers to the hadronic decays of the τ lepton, and ℓ is either an electron or a muon. The data sample corresponds to an integrated luminosity of 35.9 fb−1 collected in proton-proton collisions at s√ = 13 TeV with the CMS detector. The measured cross section is σtt¯ = 781 ± 7 (stat) ± 62 (syst) ± 20 (lumi) pb, and the ratio of the partial width Γ(t → τντb) to the total decay width of the top quark is measured to be 0.1050 ± 0.0009 (stat) ± 0.0071 (syst). This is the first measurement of the tt¯ production cross section in proton-proton collisions at s√ = 13 TeV that explicitly includes τ leptons. The ratio of the cross sections in the ℓτh and ℓℓ final states yields a value Rℓτh/ll = 0.973 ± 0.009 (stat) ± 0.066 (syst), consistent with lepton universality.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Combined search for supersymmetry with photons in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: ELSEVIER
Sirunyany AM, Tumasyan A, Adam W, et al., 2020, Search for top squark pair production in a final state with two tau leptons in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-45, ISSN: 1029-8479
A search for pair production of the supersymmetric partner of the top quark, the top squark, in proton-proton collision events at s√ = 13 TeV is presented in a final state containing hadronically decaying tau leptons and large missing transverse momentum. This final state is highly sensitive to high-tan β or higgsino-like scenarios in which decays of electroweak gauginos to tau leptons are dominant. The search uses a data set corresponding to an integrated luminosity of 77.2 fb−1, which was recorded with the CMS detector during 2016 and 2017. No significant excess is observed with respect to the background prediction. Exclusion limits at 95% confidence level are presented in the top squark and lightest neutralino mass plane within the framework of simplified models, in which top squark masses up to 1100 GeV are excluded for a nearly massless neutralino.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Performance of the reconstruction and identification of high-momentum muons in proton-proton collisions at root s=13 TeV, Journal of Instrumentation, Vol: 15, Pages: 1-56, ISSN: 1748-0221
The CMS detector at the LHC has recorded events from proton-proton collisions, with muon momenta reaching up to 1.8 TeV in the collected dimuon samples. These high-momentum muons allow direct access to new regimes in physics beyond the standard model. Because the physics and reconstruction of these muons are different from those of their lower-momentum counterparts, this paper presents for the first time dedicated studies of efficiencies, momentum assignment, resolution, scale, and showering of very high momentum muons produced at the LHC. These studies are performed using the 2016 and 2017 data sets of proton-proton collisions at √s = 13 TeV with integrated luminosities of 36.3 and 42.1 fb−1, respectively.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for Supersymmetry with a Compressed Mass Spectrum in Events with a Soft τ Lepton, a Highly Energetic Jet, and Large Missing Transverse Momentum in Proton-Proton Collisions at sqrt[s]=13 TeV., Physical Review Letters, Vol: 124, Pages: 041803-041803, ISSN: 0031-9007
The first search for supersymmetry in events with an experimental signature of one soft, hadronically decaying τ lepton, one energetic jet from initial-state radiation, and large transverse momentum imbalance is presented. These event signatures are consistent with direct or indirect production of scalar τ leptons (τ[over ˜]) in supersymmetric models that exhibit coannihilation between the τ[over ˜] and the lightest neutralino (χ[over ˜]_{1}^{0}), and that could generate the observed relic density of dark matter. The data correspond to an integrated luminosity of 77.2 fb^{-1} of proton-proton collisions at sqrt[s]=13 TeV collected with the CMS detector at the LHC in 2016 and 2017. The results are interpreted in a supersymmetric scenario with a small mass difference (Δm) between the chargino (χ[over ˜]_{1}^{±}) or next-to-lightest neutralino (χ[over ˜]_{2}^{0}), and the χ[over ˜]_{1}^{0}. The mass of the τ[over ˜] is assumed to be the average of the χ[over ˜]_{1}^{±} and χ[over ˜]_{1}^{0} masses. The data are consistent with standard model background predictions. Upper limits at 95% confidence level are set on the sum of the χ[over ˜]_{1}^{±}, χ[over ˜]_{2}^{0}, and τ[over ˜] production cross sections for Δm(χ[over ˜]_{1}^{±},χ[over ˜]_{1}^{0})=50 GeV, resulting in a lower limit of 290 GeV on the mass of the χ[over ˜]_{1}^{±}, which is the most stringent to date and surpasses the bounds from the LEP experiments.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for production of four top quarks in final states with svame-sign or multiple leptons in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: SPRINGER
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- Citations: 55
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Evidence for WW production from double-parton interactions in proton-proton collisions at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 80, Pages: 1-26, ISSN: 1124-1861
A search for WW production from double-parton scattering processes using same-charge electron-muon and dimuon events is reported, based on proton-proton collision data collected at a center-of-mass energy of 13TeV. The analyzed data set corresponds to an integrated luminosity of 77.4fb−1, collected using the CMS detector at the LHC in 2016 and 2017. Multivariate classifiers are used to discriminate between the signal and the dominant background processes. A maximum likelihood fit is performed to extract the signal cross section. This leads to the first evidence for WW production via double-parton scattering, with a significance of 3.9 standard deviations. The measured inclusive cross section is 1.41±0.28(stat)±0.28(syst)pb.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for a charged Higgs boson decaying into top and bottom quarks in events with electrons or muons in proton-proton collisions at root s=13TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-48, ISSN: 1029-8479
A search is presented for a charged Higgs boson heavier than the top quark, produced in association with a top quark, or with a top and a bottom quark, and decaying into a top-bottom quark-antiquark pair. The search is performed using proton-proton collision data collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Events are selected by the presence of a single isolated charged lepton (electron or muon) or an opposite-sign dilepton (electron or muon) pair, categorized according to the jet multiplicity and the number of jets identified as originating from b quarks. Multivariate analysis techniques are used to enhance the discrimination between signal and background in each category. The data are compatible with the standard model, and 95% confidence level upper limits of 9.6–0.01 pb are set on the charged Higgs boson production cross section times branching fraction to a top-bottom quark-antiquark pair, for charged Higgs boson mass hypotheses ranging from 200 GeV to 3 TeV. The upper limits are interpreted in different minimal supersymmetric extensions of the standard model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of nuclear modifications in W<SUP>±</SUP> boson production in pPb collisions at √<i>s</i><sub>NN</sub>=8.16 TeV, Publisher: ELSEVIER
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- Citations: 22
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