Publications
1759 results found
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Precision measurement of the W boson decay branching fractions in proton-proton collisions at ? s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, Pages: 1-31, ISSN: 1550-2368
The leptonic and inclusive hadronic decay branching fractions of the W boson are measured using proton-proton collision data collected at √s=13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb−1. Events characterized by the production of one or two W bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of b quarks. A binned maximum likelihood estimate of the W boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the W boson decaying into electron, muon, and tau lepton final states are (10.83±0.10)%, (10.94±0.08)%, and (10.77±0.21)%, respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be (10.89±0.08)% and (67.32±0.23)%, respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo–Kobayashi–Maskawa (CKM) matrix ∑ij|Vij|2=1.984±0.021, the CKM element |Vcs|=0.967±0.011, and the strong coupling constant at the W boson mass scale, αS(m2W)=0.095±0.033.
Sirunyan AM, Tumasyan A, Adam W, et al., 2022, Measurement of exclusive Υ photoproduction from protons in pPb collisions at √s<sub>NN</sub> = 5.02 TeV (vol 79, 277, 2019), EUROPEAN PHYSICAL JOURNAL C, Vol: 82, ISSN: 1434-6044
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-58, ISSN: 1029-8479
A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at s√ = 13 TeV collected in the three-year period 2016–2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb−1. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on χ∼02/χ∼±1 masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter μ up to 180 GeV with the bino mass parameter M1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for heavy resonances decaying to ZZ or ZW and axion-like particles mediating nonresonant ZZ or ZH production at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-49, ISSN: 1029-8479
A search has been performed for heavy resonances decaying to ZZ or ZW and for axion-like particles (ALPs) mediating nonresonant ZZ or ZH production, in 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 Z, W, or Higgs boson H. The analysis is sensitive to resonances with masses in the range 450 to 2000 GeV. Two categories are defined corresponding to the merged or resolved reconstruction of the hadronically decaying boson. The search is based on data collected during 2016–2018 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb−1. No significant excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-2 and spin-1 resonances are derived as functions of the resonance mass, and exclusion limits on the production of bulk graviton particles and W′ bosons are calculated in the framework of the warped extra dimensions and heavy vector triplet models, respectively. In addition, upper limits on the ALP-mediated diboson production cross section and ALP couplings to standard model particles are obtained in the framework of linear and chiral effective field theories. These are the first limits on nonresonant ALP-mediated ZZ and ZH production obtained by the LHC experiments.
Sirunyan AM, Tumasyan A, Adam W, et al., 2022, Measurement of the top quark mass with lepton+jets final states using pp collisions at √<i>s</i> = 13TeV (vol 78, 891, 2018), EUROPEAN PHYSICAL JOURNAL C, Vol: 82, ISSN: 1434-6044
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for long-lived particles decaying into muon pairs in proton-proton collisions at root s=13 TeV collected with a dedicated high-rate data stream, The Journal of High Energy Physics, Vol: 2022, Pages: 1-45, ISSN: 1029-8479
A search for long-lived particles decaying into muon pairs is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017 and 2018, corresponding to an integrated luminosity of 101 fb−1. The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No significant excess of events beyond the standard model expectation is found. Upper limits on branching fractions at 95% confidence level are set on a wide range of mass and lifetime hypotheses in beyond the standard model frameworks with the Higgs boson decaying into a pair of long-lived dark photons, or with a long-lived scalar resonance arising from a decay of a b hadron. The limits are the most stringent to date for substantial regions of the parameter space. These results can be also used to constrain models of displaced dimuons that are not explicitly considered in this paper.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for a heavy resonance decaying into a top quark and a W boson in the lepton plus jets final state at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-43, ISSN: 1029-8479
A search for a heavy resonance decaying into a top quark and a W boson in proton-proton collisions at s√ = 13 TeV is presented. The data analyzed were recorded with the CMS detector at the LHC and correspond to an integrated luminosity of 138 fb−1. The top quark is reconstructed as a single jet and the W boson, from its decay into an electron or muon and the corresponding neutrino. A top quark tagging technique based on jet clustering with a variable distance parameter and simultaneous jet grooming is used to identify jets from the collimated top quark decay. The results are interpreted in the context of two benchmark models, where the heavy resonance is either an excited bottom quark b∗ or a vector-like quark B. A statistical combination with an earlier search by the CMS Collaboration in the all-hadronic final state is performed to place upper cross section limits on these two models. The new analysis extends the lower range of resonance mass probed from 1.4 down to 0.7 TeV. For left-handed, right-handed, and vector-like couplings, b∗ masses up to 3.0, 3.0, and 3.2 TeV are excluded at 95% confidence level, respectively. The observed upper limits represent the most stringent constraints on the b∗ model to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for a right-handed W boson and a heavy neutrino in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-43, ISSN: 1029-8479
A search is presented for a right-handed W boson (WR) and a heavy neutrino (N), in a final state consisting of two same-flavor leptons (ee or μμ) and two quarks. The search is performed with the CMS experiment at the CERN LHC using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb−1. The search covers two regions of phase space, one where the decay products of the heavy neutrino are merged into a single large-area jet, and one where the decay products are well separated. The expected signal is characterized by an excess in the invariant mass distribution of the final-state objects. No significant excess over the standard model background expectations is observed. The observations are interpreted as upper limits on the product of WR production cross sections and branching fractions assuming that couplings are identical to those of the standard model W boson. For N masses mN equal to half the WR mass mWR (mN = 0.2 TeV), mWR is excluded at 95% confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channels, respectively. This analysis provides the most stringent limits on the WR mass to date.
Tumasyan A, Adam W, Bergauer T, et al., 2022, Search for low-mass dilepton resonances in Higgs boson decays to four-lepton final states in proton-proton collisions at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 82, ISSN: 1124-1861
A search for low-mass dilepton resonances in Higgs boson decays is conducted in the four-lepton final state. The decay is assumed to proceed via a pair of beyond the standard model particles, or one such particle and a Z boson. The search uses proton–proton collision data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 137fb−1, at a center-of-mass energy s√=13TeV. No significant deviation from the standard model expectation is observed. Upper limits at 95% confidence level are set on model-independent Higgs boson decay branching fractions. Additionally, limits on dark photon and axion-like particle production, based on two specific models, are reported.
Abbott R, Abbott TD, Acernese F, et al., 2022, Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run, PHYSICAL REVIEW D, Vol: 105, ISSN: 2470-0010
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Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Study of dijet events with large rapidity separation in proton-proton collisions at root s=2.76 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-46, ISSN: 1029-8479
The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at s√ = 2.76 TeV for jets with transverse momentum pT > 35 GeV and rapidity |y| < 4.7. Various dijet production cross section ratios are also measured. A veto on additional jets with pT > 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.
Sirunyan AM, Tumasyan A, Adam W, et al., 2022, Using Z boson events to study parton-medium interactions in Pb-Pb collisions, Physical Review Letters, Vol: 128, ISSN: 0031-9007
The spectra measurements of charged hadrons produced in the shower of a parton originating in the same hard scattering with a leptonically decaying Z boson are reported in lead-lead nuclei (Pb-Pb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Both Pb-Pb and pp data sets are recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 1.7 nb^{-1} and 320 pb^{-1}, respectively. Hadronic collision data with one reconstructed Z boson candidate with the transverse momentum p_{T}>30 GeV/c are analyzed. The Z boson constrains the initial energy and direction of the associated parton. In heavy ion events, azimuthal angular distributions of charged hadrons with respect to the direction of a Z boson are sensitive to modifications of the in-medium parton shower and medium response. compared to reference data from pp interactions, the results for central Pb-Pb collisions indicate a modification of the angular correlations. The measurements of the fragmentation functions and p_{T} spectra of charged particles in Z boson events, which are sensitive to medium modifications of the parton shower longitudinal structure, are also reported. Significant modifications in central Pb-Pb events compared to the pp reference data are also found for these observables.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for long-lived particles produced in association with a Z boson in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-37, ISSN: 1029-8479
A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016–2018, corresponding to an integrated luminosity of 117 fb−1. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H → SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10–100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass (≈ 15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions B(H → SS) < 20% for proper decay lengths of 10–50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.
Tumasyan A, Adam W, Bergauer T, et al., 2022, Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at s = 13 TeV, European Physical Journal C: Particles and Fields, Vol: 82, ISSN: 1124-1861
A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 16.1 fb - 1 , collected with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100 GeV are excluded and further sensitivity is explored towards higher masses.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for Wγ resonances in proton-proton collisions at s=13 TeV using hadronic decays of Lorentz-boosted W bosons, Physics Letters B, Vol: 826, ISSN: 0370-2693
A search for Wγ resonances in the mass range between 0.7 and 6.0 TeV is presented. The W boson is reconstructed via its hadronic decays, with the final-state products forming a single large-radius jet, owing to a high Lorentz boost of the W boson. The search is based on proton-proton collisiondata at √s = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, collected with the CMS detector at the LHC in 2016–2018. The Wγ mass spectrum is parameterized with a smoothly falling background function and examined for the presence of resonance-like signals. No significant excess above the predicted background is observed. Model-specific upper limits at 95% confidence level on the product of the cross section and branching fraction to the Wγ channel are set. Limits for narrow resonances and for resonances with an intrinsic width equal to 5% of their mass, for spin-0 and spin-1 hypotheses, range between 0.17 fb at 6.0 TeV and 55 fb at 0.7 TeV. These are the most restrictive limits to date on the existence of such resonances over a large range of probed masses. In specific heavy scalar (vector) triplet benchmark models, narrow resonances with masses between 0.75 (1.15) and 1.40 (1.36) TeV are excluded for a range of model parameters. Model-independent limits on the product of the cross section, signal acceptance, and branching fraction to the Wγ channel are set for minimum Wγ mass thresholds between 1.5 and 8.0 TeV.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of W-+/-gamma differential cross sections in proton-proton collisions at root s=13 TeV and effective field theory constraints, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, Pages: 1-34, ISSN: 1550-2368
Differential cross section measurements of W±γ production in proton-proton collisions at √s=13 TeV are presented. The data set used in this study was collected with the CMS detector at the CERN LHC in 2016–2018 with an integrated luminosity of 138 fb−1. Candidate events containing an electron or muon, a photon, and missing transverse momentum are selected. The measurements are compared with standard model predictions computed at next-to-leading and next-to-next-to-leading orders in perturbative quantum chromodynamics. Constraints on the presence of TeV-scale new physics affecting the WWγ vertex are determined within an effective field theory framework, focusing on the O3W operator. A simultaneous measurement of the photon transverse momentum and the azimuthal angle of the charged lepton in a special reference frame is performed. This two-dimensional approach provides up to a factor of ten more sensitivity to the interference between the standard model and the O3W contribution than using the transverse momentum alone.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, A new calibration method for charm jet identification validated with proton-proton collision events at root s=13 TeV, Journal of Instrumentation, Vol: 17, ISSN: 1748-0221
Many measurements at the LHC require efficient identification of heavy-flavour jets, i.e. jets originating from bottom (b) or charm (c) quarks. An overview of the algorithms used to identify c jets is described and a novel method to calibrate them is presented. This new method adjusts the entire distributions of the outputs obtained when the algorithms are applied to jets of different flavours. It is based on an iterative approach exploiting three distinct control regions that are enriched with either b jets, c jets, or light-flavour and gluon jets. Results are presented in the form of correction factors evaluated using proton-proton collision data with an integrated luminosity of 41.5 fb-1 at √s = 13 TeV, collected by the CMS experiment in 2017. The closure of the method is tested by applying the measured correction factors on simulated data sets and checking the agreement between the adjusted simulation and collision data. Furthermore, a validation is performed by testing the method on pseudodata, which emulate various mismodelling conditions. The calibrated results enable the use of the full distributions of heavy-flavour identification algorithm outputs, e.g. as inputs to machine-learning models. Thus, they are expected to increase the sensitivity of future physics analyses.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of the inclusive and differential Higgs boson production cross sections in the decay mode to a pair of τ Leptons in pp collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 128, ISSN: 0031-9007
Measurements of the inclusive and differential fiducial cross sections of the Higgs boson are presented, using the τ lepton decay channel. The differential cross sections are measured as functions of the Higgs boson transverse momentum, jet multiplicity, and transverse momentum of the leading jet in the event, if any. The analysis is performed using proton-proton collision data collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb^{-1}. These are the first differential measurements of the Higgs boson cross section in the final state of two τ leptons. In final states with a large jet multiplicity or with a Lorentz-boosted Higgs boson, these measurements constitute a significant improvement over measurements performed in other final states.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for heavy resonances decaying to WW, WZ, or WH boson pairs in a final state consisting of a lepton and a large-radius jet in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, Pages: 1-29, ISSN: 1550-2368
A search for new heavy resonances decaying to pairs of bosons (WW, WZ, or WH) is presented. The analysis uses data from proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb−1. One of the bosons is required to be a W boson decaying to an electron or muon and a neutrino, while the other boson is required to be reconstructed as a single jet with mass and substructure compatible with a quark pair from a W, Z, or Higgs boson decay. The search is performed in the resonance mass range between 1.0 and 4.5 TeV and includes a specific search for resonances produced via vector boson fusion. The signal is extracted using a two-dimensional maximum likelihood fit to the jet mass and the diboson invariant mass distributions. No significant excess is observed above the estimated background. Model-independent upper limits on the production cross sections of spin-0, spin-1, and spin-2 heavy resonances are derived as functions of the resonance mass and are interpreted in the context of bulk radion, heavy vector triplet, and bulk graviton models. The reported bounds are the most stringent to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for flavor-changing neutral current interactions of the top quark and the Higgs boson decaying to a bottom quark-antiquark pair at root s=13 TeV, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2022, ISSN: 1029-8479
A search for flavor-changing neutral current interactions of the top quark (t) and the Higgs boson (H) is presented. The search is based on a data sample corresponding to an integrated luminosity of 137 fb−1 recorded by the CMS experiment at the LHC in proton-proton collisions at s√ = 13 TeV. Events containing exactly one lepton (muon or electron) and at least three jets, among which at least two are identified as originating from the hadronization of a bottom quark, are analyzed. A set of deep neural networks is used for kinematic event reconstruction, while boosted decision trees distinguish the signal from the background events. No significant excess over the background predictions is observed, and upper limits on the signal production cross sections are extracted. These limits are interpreted in terms of top quark decay branching fractions (B) to the Higgs boson and an up (u) or a charm quark (c). Assuming one nonvanishing extra coupling at a time, the observed (expected) upper limits at 95% confidence level are B(t → Hu) < 0.079 (0.11)% and B(t → Hc) < 0.094 (0.086)%.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement and QCD analysis of double-differential inclusive jet cross sections in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, ISSN: 1029-8479
A measurement of the inclusive jet production in proton-proton collisions at the LHC at s√ = 13 TeV is presented. The double-differential cross sections are measured as a function of the jet transverse momentum pT and the absolute jet rapidity |y|. The anti-kT clustering algorithm is used with distance parameter of 0.4 (0.7) in a phase space region with jet pT from 97 GeV up to 3.1 TeV and |y| < 2.0. Data collected with the CMS detector are used, corresponding to an integrated luminosity of 36.3 fb−1 (33.5 fb−1). The measurement is used in a comprehensive QCD analysis at next-to-next-to-leading order, which results in significant improvement in the accuracy of the parton distributions in the proton. Simultaneously, the value of the strong coupling constant at the Z boson mass is extracted as αS(mZ) = 0.1170±0.0019. For the first time, these data are used in a standard model effective field theory analysis at next-to-leading order, where parton distributions and the QCD parameters are extracted simultaneously with imposed constraints on the Wilson coefficient c1 of 4-quark contact interactions.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, ISSN: 1029-8479
Inclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data sample corresponding to an integrated luminosity of 138 fb−1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of 87.9+7.5−7.3(stat)+7.3−6.0(syst) fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as 2.37+0.56−0.42(stat)+0.27−0.13(syst). Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0.54 ± 0.16 (stat) ± 0.06 (syst), in agreement with SM predictions.
Tumasyan A, Adam W, Bergauer T, et al., 2022, Fragmentation of jets containing a prompt J/psi meson in PbPb and pp collisions at root s(NN)=5.02 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 825, Pages: 1-25, ISSN: 0370-2693
Jets containing a prompt J/ψ meson are studied in lead-lead collisions at a nucleon-nucleon center-ofmass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transversemomentum range of 30 < pT < 40 GeV. The J/ψ yield in these jets is evaluated as a function of the jetfragmentation variable z, the ratio of the J/ψ pT to the jet pT. The nuclear modification factor, RAA,is then derived by comparing the yield in lead-lead collisions to the corresponding expectation basedon proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the J/ψyield shows a dependence on z, indicating that the interaction of the J/ψ with the quark-gluon plasmaformed in heavy ion collisions depends on the fragmentation that gives rise to the J/ψ meson.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Search for long-lived particles decaying to leptons with large impact parameter in proton-proton collisions at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 82, Pages: 1-32, ISSN: 1124-1861
A search for new long-lived particles decaying to leptons using proton–proton collision data produced by the CERN LHC at s√=13TeV is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10cm and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113)fb−1 in the ee channel (eμ and μμ channels). The search is designed to be sensitive to a wide range of models with displaced eμ, ee, and μμ final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Study of quark and gluon jet substructure in Z plus jet and dijet events from pp collisions, The Journal of High Energy Physics, Vol: 2022, Pages: 1-54, ISSN: 1029-8479
Measurements of jet substructure describing the composition of quark- andgluon-initiated jets are presented. Proton-proton (pp) collision data at √s = 13 TeVcollected with the CMS detector are used, corresponding to an integrated luminosity of35.9 fb−1. Generalized angularities are measured that characterize the jet substructureand distinguish quark- and gluon-initiated jets. These observables are sensitive to thedistributions of transverse momenta and angular distances within a jet. The analysis isperformed using a data sample of dijet events enriched in gluon-initiated jets, and, for thefirst time, a Z+jet event sample enriched in quark-initiated jets. The observables are measured in bins of jet transverse momentum, and as a function of the jet radius parameter.Each measurement is repeated applying a “soft drop” grooming procedure that removessoft and large angle radiation from the jet. Using these measurements, the ability of variousmodels to describe jet substructure is assessed, showing a clear need for improvements inMonte Carlo generators.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2022, Measurement of double-parton scattering in inclusive production of four jets with low transverse momentum in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2022, Pages: 1-61, ISSN: 1029-8479
A measurement of inclusive four-jet production in proton-proton collisions ata center-of-mass energy of 13 TeV is presented. The transverse momenta of jets within|η| < 4.7 are required to exceed 35, 30, 25, and 20 GeV for the first-, second-, third-, andfourth-leading jet, respectively. Differential cross sections are measured as functions of thejet transverse momentum, jet pseudorapidity, and several other observables that describethe angular correlations between the jets. The measured distributions show sensitivityto different aspects of the underlying event, parton shower modeling, and matrix elementcalculations. In particular, the interplay between angular correlations caused by partonshower and double-parton scattering contributions is shown to be important. The doubleparton scattering contribution is extracted by means of a template fit to the data, usingdistributions for single-parton scattering obtained from Monte Carlo event generators anda double-parton scattering distribution constructed from inclusive single-jet events in data.The effective double-parton scattering cross section is calculated and discussed in view ofprevious measurements and of its dependence on the models used to describe the singleparton scattering background
Sirunyan AM, Tumasyan A, Adam W, et al., 2022, Evidence for X(3872) in Pb-Pb collisions and studies of its prompt production at sqrt[s_{NN}]=5.02 TeV., Physical Review Letters, Vol: 128, Pages: 1-18, ISSN: 0031-9007
The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of sqrt[s_{NN}]=5.02 TeV per nucleon pair, using the decay chain X(3872)→J/ψπ^{+}π^{-}→μ^{+}μ^{-}π^{+}π^{-}. The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 nb^{-1}. The measurement is performed in the rapidity and transverse momentum ranges |y|<1.6 and 15<p_{T}<50 GeV/c. The significance of the inclusive X(3872) signal is 4.2 standard deviations. The prompt X(3872) to ψ2S yield ratio is found to be ρ^{Pb-Pb}=1.08±0.49(stat)±0.52(syst), to be compared with typical values of 0.1 for pp collisions. This result provides a unique experimental input to theoretical models of the X(3872) production mechanism, and of the nature of this exotic state.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Search for long-lived particles decaying in the CMS end cap muon detectors in proton-proton collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 127, Pages: 261804-261804, ISSN: 0031-9007
A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb^{-1} of proton-proton collisions at sqrt[s]=13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and τ^{+}τ^{-} are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurement of the inclusive and differential t(t)over-bar gamma cross sections in the single-lepton channel and EFT interpretation at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-59, ISSN: 1029-8479
The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set, corresponding to an integrated luminosity of 137 fb−1, was recorded by the CMS experiment during the 2016–2018 data taking of the LHC. The measurements are performed in a fiducial volume defined at the particle level. Events with an isolated, highly energetic lepton, at least three jets from the hadronization of quarks, among which at least one is b tagged, and one isolated photon are selected. The inclusive fiducial tt¯γ cross section, for a photon with transverse momentum greater than 20 GeV and pseudorapidity |η| < 1.4442, is measured to be 798 ± 7(stat) ± 48(syst) fb, in good agreement with the prediction from the standard model at next-to-leading order in quantum chromodynamics. The differential cross sections are also measured as a function of several kinematic observables and interpreted in the framework of the standard model effective field theory (EFT), leading to the most stringent direct limits to date on anomalous electromagnetic dipole moment interactions of the top quark and the photon.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-57, ISSN: 1029-8479
A measurement of the top quark mass is performed using a data sample enriched with single top quark events produced in the t channel. The study is based on proton- proton collision data, corresponding to an integrated luminosity of 35.9 fb−1, recorded at s√ = 13 TeV by the CMS experiment at the LHC in 2016. Candidate events are selected by requiring an isolated high-momentum lepton (muon or electron) and exactly two jets, of which one is identified as originating from a bottom quark. Multivariate discriminants are designed to separate the signal from the background. Optimized thresholds are placed on the discriminant outputs to obtain an event sample with high signal purity. The top quark mass is found to be 172.13+0.76−0.77 GeV, where the uncertainty includes both the statistical and systematic components, reaching sub-GeV precision for the first time in this event topology. The masses of the top quark and antiquark are also determined separately using the lepton charge in the final state, from which the mass ratio and difference are determined to be 0.9952+0.0079−0.0104 and 0.83+1.79−1.35 GeV, respectively. The results are consistent with CPT invariance.
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