Publications
1515 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for lepton-flavor violating decays of the Higgs boson in the mu tau and e tau final states in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-31, ISSN: 1550-2368
A search is presented for lepton-flavor violating decays of the Higgs boson to μτ and eτ. The dataset corresponds to an integrated luminosity of 137 fb−1 collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, B(H→μτ)<0.15(0.15)% and B(H→eτ)<0.22(0.16)% at 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Hard color-singlet exchange in dijet events in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-35, ISSN: 1550-2368
Events where the two leading jets are separated by a pseudorapidity interval devoid of particle activity, known as jet-gap-jet events, are studied in proton-proton collisions at √s=13 TeV. The signature is expected from hard color-singlet exchange. Each of the highest transverse momentum (pT) jets must have pjetT>40 GeV and pseudorapidity 1.4<|ηjet|<4.7, with ηjet1ηjet2<0, where jet1 and jet2 are the leading and subleading jets in pT, respectively. The analysis is based on data collected by the CMS and TOTEM experiments during a low luminosity, high-β∗ run at the CERN LHC in 2015, with an integrated luminosity of 0.66 pb−1. Events with a low number of charged particles with pT>0.2 GeV in the interval |η|<1 between the jets are observed in excess of calculations that assume only color-exchange. The fraction of events produced via color-singlet exchange, fCSE, is measured as a function of pjet2T, the pseudorapidity difference between the two leading jets, and the azimuthal angular separation between the two leading jets. The fraction fCSE has values of 0.4–1.0%. The results are compared with previous measurements and with predictions from perturbative quantum chromodynamics. In addition, the first study of jet-gap-jet events detected in association with an intact proton using a subsample of events with an integrated luminosity of 0.40 pb−1 is presented. The intact protons are detected with the Roman pot detectors of the TOTEM experiment. The fCSE in this sample is 2.91±0.70(stat)+1.08−1.01(syst) times larger than that for inclusive dijet production in dijets with similar kinematics.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for top squarks in final states with two top quarks and several light-flavor jets in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-26, ISSN: 1550-2368
Many new physics models, including versions of supersymmetry characterized by R-parity violation (RPV), compressed mass spectra, long decay chains, or additional hidden sectors, predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for new physics in events with two top quarks and additional jets are reported. The search is performed using events with at least seven jets and exactly one electron or muon. No requirement on missing transverse momentum is imposed. The study is based on a sample of proton-proton collisions at √s=13TeV corresponding to 137 fb−1 of integrated luminosity collected with the CMS detector at the LHC in 2016–2018. The data are used to determine best fit values and upper limits on the cross section for pair production of top squarks in scenarios of RPV and stealth supersymmetry. Top squark masses up to 670 (870) GeV are excluded at 95% confidence level for the RPV (stealth) scenario, and the maximum observed local signal significance is 2.8 standard deviations for the RPV scenario with top squark mass of 400 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the azimuthal anisotropy of and mesons in PbPb collisions at sNN=5.02TeV, Physics Letters B, Vol: 819, Pages: 1-23, ISSN: 0370-2693
The second-order Fourier coefficients (v2) characterizing the azimuthal distributions of Υ(1S) and Υ(2S)mesons produced in PbPb collisions at √sNN = 5.02 TeV are studied. The Υ mesons are reconstructed intheir dimuon decay channel, as measured by the CMS detector. The collected data set corresponds toan integrated luminosity of 1.7 nb−1. The scalar product method is used to extract the v2 coefficientsof the azimuthal distributions. Results are reported for the rapidity range |y| < 2.4, in the transversemomentum interval 0 < pT < 50 GeV/c, and in three centrality ranges of 10–30%, 30–50% and 50–90%.In contrast to the J/ψ mesons, the measured v2 values for the Υ mesons are found to be consistent withzero.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at root s(NN)=5.02 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 819, Pages: 1-23, ISSN: 0370-2693
The second-order Fourier coefficients (v2) characterizing the azimuthal distributions of Υ(1S) and Υ(2S)mesons produced in PbPb collisions at √sNN = 5.02 TeV are studied. The Υ mesons are reconstructed intheir dimuon decay channel, as measured by the CMS detector. The collected data set corresponds toan integrated luminosity of 1.7 nb−1. The scalar product method is used to extract the v2 coefficientsof the azimuthal distributions. Results are reported for the rapidity range |y| < 2.4, in the transversemomentum interval 0 < pT < 50 GeV/c, and in three centrality ranges of 10–30%, 30–50% and 50–90%.In contrast to the J/ψ mesons, the measured v2 values for the Υ mesons are found to be consistent withzero.
Collaboration CMS, 2021, Search for a heavy vector resonance decaying to a Z boson and a Higgs boson in proton-proton collisions at s√=13TeV, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-31, ISSN: 1124-1861
A search is presented for a heavy vector resonance decaying into a Z boson and the standard model Higgs boson, where the Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137fb−1. Upper limits are derived on the production of a narrow heavy resonance Z′, and a mass below 3.5 and 3.7TeV is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet Z′ model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3fb for a Z′ mass between 0.8 and 4.6TeV, respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for the rare decay of the W boson into a pion and a photon in proton-proton collisions at s=13TeV, Physics Letters B, Vol: 819, Pages: 1-24, ISSN: 0370-2693
A search is performed for the rare decay W± → π±γ in proton-proton collisions at √s = 13 TeV. Datacorresponding to an integrated luminosity of 137 fb−1 were collected during 2016 to 2018 with the CMSdetector. This analysis exploits a novel search strategy based on W boson production in top quark pairevents. An inclusive search for the W± → π±γ decay is not optimal at the LHC because of the hightrigger thresholds. Instead, a trigger selection is exploited in which the W boson originating from one ofthe top quarks is used to tag the event in a leptonic decay. The W boson emerging from the other topquark is used to search for the W± → π±γ signature. Such decays are characterized by an isolatedtrack pointing to a large energy deposit, and by an isolated photon of large transverse momentum.The presence of b quark jets reduces the background from the hadronization of light-flavor quarks andgluons. The W± → π±γ decay is not observed. An upper exclusion limit is set to this branching fraction,corresponding to 1.50 × 10−5 at 95% confidence level, whereas the expected upper exclusion limit is0.85+0.52−0.29 × 10−5.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for singly and pair-produced leptoquarks coupling to third-generation fermions in proton-proton collisions at s=13 TeV, Physics Letters B, Vol: 819, Pages: 1-27, ISSN: 0370-2693
A search for leptoquarks produced singly and in pairs in proton-proton collisions is presented. Weconsider the leptoquark (LQ) to be a scalar particle of charge −1/3e coupling to a top quark plus atau lepton (tτ) or a bottom quark plus a neutrino (bν), or a vector particle of charge +2/3e, coupling totν or bτ. These choices are motivated by models that can explain a series of anomalies observed in themeasurement of B meson decays. In this analysis the signatures tτνb and tτν are probed, using datarecorded by the CMS experiment at the CERN LHC at √s = 13 TeV and that correspond to an integratedluminosity of 137 fb−1. These signatures have not been previously explored in a dedicated search. Thedata are found to be in agreement with the standard model prediction. Lower limits at 95% confidencelevel are set on the LQ mass in the range 0.98–1.73 TeV, depending on the LQ spin and its coupling λ toa lepton and a quark, and assuming equal couplings for the two LQ decay modes considered. These arethe most stringent constraints to date on the existence of leptoquarks in this scenario.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector boson pairs in proton–proton collisions at s√=13TeV, The European Physical Journal C, Vol: 81, Pages: 1-29, ISSN: 1434-6044
A search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector bosons, using proton–proton collisions at s√=13TeV at the LHC, is reported. The data sample corresponds to an integrated luminosity of 137fb−1 collected with the CMS detector. Events are selected by requiring two or three electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. No excess of events with respect to the standard model background predictions is observed. Model independent upper limits at 95% confidence level are 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 200 to 3000GeV. The results are interpreted in the context of the Georgi–Machacek model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for long-lived particles using displaced jets in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-38, ISSN: 1550-2368
An inclusive search is presented for long-lived particles using displaced jets. The search uses a data sample collected with the CMS detector at the CERN LHC in 2017 and 2018, from proton-proton collisions at a center-of-mass energy of 13 TeV. The results of this search are combined with those of a previous search using a data sample collected with the CMS detector in 2016, yielding a total integrated luminosity of 132 fb−1. The analysis searches for the distinctive topology of displaced tracks and displaced vertices associated with a dijet system. For a simplified model, where pair-produced long-lived neutral particles decay into quark-antiquark pairs, pair production cross sections larger than 0.07 fb are excluded at 95% confidence level (C.L.) for long-lived particle masses larger than 500 GeV and mean proper decay lengths between 2 and 250 mm. For a model where the standard model-like Higgs boson decays to two long-lived scalar particles that each decays to a quark-antiquark pair, branching fractions larger than 1% are excluded at 95% C.L. for mean proper decay lengths between 1 mm and 340 mm. A group of supersymmetric models with pair-produced long-lived gluinos or top squarks decaying into various final-state topologies containing displaced jets is also tested. Gluino masses up to 2500 GeV and top squark masses up to 1600 GeV are excluded at 95% C.L. for mean proper decay lengths between 3 and 300 mm. The highest lower bounds on mass reach 2600 GeV for long-lived gluinos and 1800 GeV for long-lived top squarks. These are the most stringent limits to date on these models.Figure
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for resonant and nonresonant new phenomena in high-mass dilepton final states at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-62, ISSN: 1029-8479
A search is presented for physics beyond the standard model (SM) using electron or muon pairs with high invariant mass. A data set of proton-proton collisions collected by the CMS experiment at the LHC at s√ = 13 TeV from 2016 to 2018 corresponding to a total integrated luminosity of up to 140 fb−1 is analyzed. No significant deviation is observed with respect to the SM background expectations. Upper limits are presented on the ratio of the product of the production cross section and the branching fraction to dileptons of a new narrow resonance to that of the Z boson. These provide the most stringent lower limits to date on the masses for various spin-1 particles, spin-2 gravitons in the Randall-Sundrum model, as well as spin-1 mediators between the SM and dark matter particles. Lower limits on the ultraviolet cutoff parameter are set both for four-fermion contact interactions and for the Arkani-Hamed, Dimopoulos, and Dvali model with large extra dimensions. Lepton flavor universality is tested at the TeV scale for the first time by comparing the dimuon and dielectron mass spectra. No significant deviation from the SM expectation of unity is observed.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-87, ISSN: 1029-8479
Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at s√ = 13 TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb−1. Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12±0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Performance of the CMS muon trigger system in proton-proton collisions at root s=13 TeV, Journal of Instrumentation, Vol: 16, Pages: 1-54, ISSN: 1748-0221
The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015–2018) the LHC achieved instantaneous luminosities as high as 2 × 1034 while delivering proton-proton collisions at √(s) = 13. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40MHz to about 1kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstruction and identification algorithms since the end of Run 1 and throughout the Run 2 data-taking period. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. In this paper, the algorithms used in 2015 and 2016 and their improvements throughout 2017 and 2018 are described. Measurements of the CMS muon trigger performance for this data-taking period are presented, including efficiencies, transverse momentum resolution, trigger rates, and the purity of the selected muon sample. This paper focuses on the single- and double-muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, MUSiC: a model-unspecific search for new physics in proton–proton collisions at s√=13TeV, The European Physical Journal C, Vol: 81, Pages: 1-49, ISSN: 1434-6044
Results of the Model Unspecific Search in CMS (MUSiC), using proton–proton collision data recorded at the LHC at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 35.9fb−1, are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the Wγ production cross section in proton-proton collisions at sqrt[s]=13 TeV and constraints on effective field theory coefficients, Physical Review Letters, Vol: 126, ISSN: 0031-9007
A fiducial cross section for Wγ production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb^{-1} of data collected using the CMS detector at the LHC. The W→eν and μν decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Observation of a new excited beauty strange baryon decaying to Ξ_{b}^{-}π^{+}π^{-}, Physical Review Letters, Vol: 126, ISSN: 0031-9007
The Ξ_{b}^{-}π^{+}π^{-} invariant mass spectrum is investigated with an event sample of proton-proton collisions at sqrt[s]=13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140 fb^{-1}. The ground state Ξ_{b}^{-} is reconstructed via its decays to J/ψΞ^{-} and J/ψΛK^{-}. A narrow resonance, labeled Ξ_{b}(6100)^{-}, is observed at a Ξ_{b}^{-}π^{+}π^{-} invariant mass of 6100.3±0.2(stat)±0.1(syst)±0.6(Ξ_{b}^{-}) MeV, where the last uncertainty reflects the precision of the Ξ_{b}^{-} baryon mass. The upper limit on the Ξ_{b}(6100)^{-} natural width is determined to be 1.9 MeV at 95% confidence level. The low Ξ_{b}(6100)^{-} signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Ξ_{c} baryon states, the new Ξ_{b}(6100)^{-} resonance and its decay sequence are consistent with the orbitally excited Ξ_{b}^{-} baryon, with spin and parity quantum numbers J^{P}=3/2^{-}.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of production cross sections of the Higgs boson in the four-lepton final state in proton–proton collisions at s√=13TeV, The European Physical Journal C, Vol: 81, Pages: 1-47, ISSN: 1434-6044
Production cross sections of the Higgs boson are measured in the H→ZZ→4ℓ (ℓ=e,μ) decay channel. A data sample of proton–proton collisions at a center-of-mass energy of 13TeV, collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137fb−1 is used. The signal strength modifier μ, defined as the ratio of the Higgs boson production rate in the 4ℓ channel to the standard model (SM) expectation, is measured to be μ=0.94±0.07(stat)+0.09−0.08(syst) at a fixed value of mH=125.38GeV. The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H→4ℓ process is measured to be 2.84+0.23−0.22(stat)+0.26−0.21(syst)fb, which is compatible with the SM prediction of 2.84±0.15fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, First measurement of large area jet transverse momentum spectra in heavy-ion collisions, The Journal of High Energy Physics, Vol: 2021, Pages: 1-48, ISSN: 1029-8479
Jet production in lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is studied with the CMS detector at the LHC, using PbPb and pp data samples corresponding to integrated luminosities of 404 μb−1 and 27.4 pb−1, respectively. Jets with different areas are reconstructed using the anti-kT algorithm by varying the distance parameter R. The measurements are performed using jets with transverse momenta (pT) greater than 200 GeV and in a pseudorapidity range of |η| < 2. To reveal the medium modification of the jet spectra in PbPb collisions, the properly normalized ratio of spectra from PbPb and pp data is used to extract jet nuclear modification factors as functions of the PbPb collision centrality, pT and, for the first time, as a function of R up to 1.0. For the most central collisions, a strong suppression is observed for high-pT jets reconstructed with all distance parameters, implying that a significant amount of jet energy is scattered to large angles. The dependence of jet suppression on R is expected to be sensitive to both the jet energy loss mechanism and the medium response, and so the data are compared to several modern event generators and analytic calculations. The models considered do not fully reproduce the data.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of the differential cross sections of the production of Z plus jets and gamma plus jets and of Z boson emission collinear with a jet in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-43, ISSN: 1029-8479
Measurements of the differential cross sections of Z + jets and γ + jets production, and their ratio, are presented as a function of the boson transverse momentum. Measurements are also presented of the angular distribution between the Z boson and the closest jet. The analysis is based on pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb−1 recorded by the CMS experiment at the LHC. The results, corrected for detector effects, are compared with various theoretical predictions. In general, the predictions at higher orders in perturbation theory show better agreement with the measurements. This work provides the first measurement of the ratio of the differential cross sections of Z + jets and γ + jets production at 13 TeV, as well as the first direct measurement of Z bosons emitted collinearly with a jet.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the Z boson differential production cross section using its invisible decay mode (Z -> nu(nu)over-bar) in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-43, ISSN: 1029-8479
Measurements of the total and differential fiducial cross sections for the Z boson decaying into two neutrinos are presented at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected by the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb−1. In these measurements, events are selected containing an imbalance in transverse momentum and one or more energetic jets. The fiducial differential cross section is measured as a function of the Z boson transverse momentum. The results are combined with a previous measurement of charged-lepton decays of the Z boson. The measured total fiducial cross section for events with Z boson transverse momentum greater than 200 GeV is 3000+180−170 fb.Measurements of the total and differential fiducial cross sections for the Z boson decaying into two neutrinos are presented at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected by the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb−1. In these measurements, events are selected containing an imbalance in transverse momentum and one or more energetic jets. The fiducial differential cross section is measured as a function of the Z boson transverse momentum. The results are combined with a previous measurement of charged-lepton decays of the Z boson. The measured total fiducial cross section for events with Z boson transverse momentum greater than 200 GeV is 3000+180−170 fb.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Study of Drell-Yan dimuon production in proton-lead collisions at root s(NN )=8.16 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-47, ISSN: 1029-8479
Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data sample recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb−1. The differential cross section as a function of the dimuon mass is measured in the range 15–600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15–60 GeV and 60–120 GeV, and ratios for the p-going over the Pb-going beam directions are built. In both mass ranges, the differential cross sections as functions of the dimuon transverse momentum pT and of a geometric variable ϕ* are measured, where ϕ* highly correlates with pT but is determined with higher precision. In the Z mass region, the rapidity dependence of the data indicate a modification of the distribution of partons within a lead nucleus as compared to the proton case. The data are more precise than predictions based upon current models of parton distributions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, In-medium modification of dijets in PbPb collisions at root s(NN)=5.02 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-44, ISSN: 1029-8479
Modifications to the distribution of charged particles with respect to high transverse momentum (pT) jets passing through a quark-gluon plasma are explored using the CMS detector. Back-to-back dijets are analyzed in lead-lead and proton-proton collisions at sNN−−−√ = 5.02 TeV via correlations of charged particles in bins of relative pseudorapidity and angular distance from the leading and subleading jet axes. In comparing the lead-lead and proton-proton collision results, modifications to the charged-particle relative distance distribution and to the momentum distributions around the jet axis are found to depend on the dijet momentum balance xj , which is the ratio between the subleading and leading jet pT. For events with xj ≈ 1, these modifications are observed for both the leading and subleading jets. However, while subleading jets show significant modifications for events with a larger dijet momentum imbalance, much smaller modifications are found for the leading jets in these events.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of prompt D-0 and D-0 meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at root S-NN=5.02 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 816, Pages: 1-25, ISSN: 0370-2693
The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapiditydependent difference (v2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow,v2) between D0 (uc) and D0 (uc) mesons. Motivated by the search for evidence of this field, the CMSdetector at the LHC is used to perform the first measurement of v2. The rapidity-averaged value isfound to be v2 = 0.001±0.001 (stat)±0.003 (syst) in PbPb collisions at √sNN = 5.02 TeV. In addition,the influence of the collision geometry is explored by measuring the D0 and D0mesons v2 and triangularflow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measureof the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0 meson v2 values isobserved, while the v3 is largely independent of centrality. These trends are consistent with expectationsof flow driven by the initial-state geometry.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the C P-violating phase φs in theB0s → J/ψφ(1020) → μ+μ− K+K− channel in proton-proton collisionsat √s = 13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 816, Pages: 1-27, ISSN: 0370-2693
The C P-violating weak phase φs and the decay width difference s between the light and heavy B0smass eigenstates are measured with the CMS detector at the LHC in a sample of 48 500 reconstructedB0s → J/ψ φ(1020) → μ+μ− K+K− events. The measurement is based on a data sample correspondingto an integrated luminosity of 96.4 fb−1, collected in proton-proton collisions at √s = 13 TeV in2017–2018. To extract the values of φs and s, a time-dependent and flavor-tagged angular analysisof the μ+μ−K+K− final state is performed. The analysis employs a dedicated tagging trigger and anovel opposite-side muon flavor tagger based on machine learning techniques. The measurement yieldsφs = −11±50 (stat)±10 (syst) mrad and s = 0.114±0.014 (stat)±0.007 (syst) ps−1, in agreement withthe standard model predictions. When combined with the previous CMS measurement at √s = 8 TeV,the following values are obtained: φs = −21 ± 44 (stat) ± 10 (syst) mrad, s = 0.1032 ± 0.0095 (stat) ±0.0048 (syst) ps−1, a significant improvement over the 8 TeV result.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of b jet shapes in proton-proton collisions at root s=5.02 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-35, ISSN: 1029-8479
We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data sample used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb−1. To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with b jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the pythia and herwig++ event generators.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC, Journal of Instrumentation, Vol: 16, Pages: 1-82, ISSN: 1748-0221
The performance is presented of the reconstruction and identification algorithms for electrons and photons with the CMS experiment at the LHC. The reported results are based on proton-proton collision data collected at a center-of-mass energy of 13 TeV and recorded in 2016–2018, corresponding to an integrated luminosity of 136 fb^-1. Results obtained from lead-lead collision data collected at √(sNN)=5.02 TeV are also presented. Innovative techniques are used to reconstruct the electron and photon signals in the detector and to optimize the energy resolution. Events with electrons and photons in the final state are used to measure the energy resolution and energy scale uncertainty in the recorded events. The measured energy resolution for electrons produced in Z boson decays in proton-proton collision data ranges from 2 to 5%, depending on electron pseudorapidity and energy loss through bremsstrahlung in the detector material. The energy scale in the same range of energies is measured with an uncertainty smaller than 0.1 (0.3)% in the barrel (endcap) region in proton-proton collisions and better than 1 (3)% in the barrel (endcap) region in heavy ion collisions. The timing resolution for electrons from Z boson decays with the full 2016–2018 proton-proton collision data set is measured to be 200 ps.
Abi B, Acciarri R, Acero MA, et al., 2021, Supernova neutrino burst detection with the Deep Underground Neutrino Experiment, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-26, ISSN: 1124-1861
The Deep Underground Neutrino Experiment (DUNE), a 40-kton underground liquid argon time projection chamber experiment, will be sensitive to the electron-neutrino flavor component of the burst of neutrinos expected from the next Galactic core-collapse supernova. Such an observation will bring unique insight into the astrophysics of core collapse as well as into the properties of neutrinos. The general capabilities of DUNE for neutrino detection in the relevant few- to few-tens-of-MeV neutrino energy range will be described. As an example, DUNE’s ability to constrain the νe spectral parameters of the neutrino burst will be considered.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of single-diffractive dijet production in proton-proton collisions at √<i>s</i> = 8 TeV with the CMS and TOTEM experiments (vol 80, 1164, 2020), EUROPEAN PHYSICAL JOURNAL C, Vol: 81, ISSN: 1434-6044
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Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Angular analysis of the decay B+-> K*(892)(+)mu(+)mu(-) in proton-proton collisions at root s=8 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-35, ISSN: 1029-8479
Angular distributions of the decay B+ → K∗(892)+μ+μ− are studied using events collected with the CMS detector in s√ = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb−1. The forward-backward asymmetry of the muons and the longitudinal polarization of the K∗(892)+ meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for supersymmetry in final states with two oppositely charged same-flavor leptons and missing transverse momentum in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-62, ISSN: 1029-8479
A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data sample of proton-proton collisions at s√ = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass; a kinematic edge in the invariant mass distribution of the lepton pair; and the nonresonant production of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1870 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios.
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