2019, Stojanovic, M., Sirunyan, A. M., Tumasyan, A., Adam, W., Matveev, V., Chadeeva, M., Parygin, P., Philippov, D., Polikarpov, S., Popova, E., Rusinov, V., Azarkin, M., Dremin, I., Kirakosyan, M., Матвеев, Виктор Анатольевич, Чадеева, Марина Валентиновна, Поликарпов, Сергей Михайлович, Русинов, Владимир Юрьевич

New measurements of anisotropic flow in XeXe collisions at a center-of-mass energy of 5.44 TeV per nucleon pair, collected by the CMS experiment at the LHC, are presented. The v(2), v(3) and v(4) Fourier coefficients of the anisotropic azimuthal distribution are obtained employing three different analysis techniques: two-particle correlations, the scalar product method, and multiparticle cumulants, which have different sensitivities to non-flow and flow fluctuation effects. The results are shown as a function of transverse momentum (P-T) for various centrality selections, and compared with corresponding results from PbPb collisions. These new measurements in a smaller nucleus-nucleus system than PbPb provide additional insights into the system-size dependence of the collective flow induced by the dominant collision geometry and its fluctuations. In particular, these results, compared to theoretical predictions and Monte Carlo generators, will provide important details on the system size dependence of the medium response in heavy ion collisions. They also offer a unique opportunity to study the onset of flow from small to large systems.

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Chadeeva, M., Parygin, P., Philippov, D., Popova, E., Rusinov, V., Матвеев, Виктор Анатольевич, Чадеева, Марина Валентиновна, Русинов, Владимир Юрьевич

© 2020, The Author(s).A search for lepton flavour violating decays of a neutral non-standard-model Higgs boson in the μτ and eτ decay modes is presented. The search is based on proton-proton collisions at a center of mass energy s = 13 TeV collected with the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb−1. The τ leptons are reconstructed in the leptonic and hadronic decay modes. No signal is observed in the mass range 200–900 GeV. At 95% confidence level, the observed (expected) upper limits on the production cross section multiplied by the branching fraction vary from 51.9 (57.4) fb to 1.6 (2.1) fb for the μτ and from 94.1 (91.6) fb to 2.3 (2.3) fb for the eτ decay modes. [Figure not available: see fulltext.].

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Bychkova, O., Chistov, R., Danilov, M., Polikarpov, S., Tarkovskii, E., Матвеев, Виктор Анатольевич, Чистов, Руслан Николаевич, Данилов, Михаил Владимирович, Поликарпов, Сергей Михайлович

© 2020 The Author(s)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 (MS‾) renormalization scheme is extracted from a comparison of the differential top quark-antiquark (tt¯) cross section as a function of the invariant mass of the tt¯ 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 tt¯ 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 35.9fb−1. 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.

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Chadeeva, M., Parygin, P., Philippov, D., Polikarpov, S., Popova, E., Rusinov, V., Dremin, I., Матвеев, Виктор Анатольевич, Чадеева, Марина Валентиновна, Поликарпов, Сергей Михайлович, Русинов, Владимир Юрьевич

© 2019 The Author(s)Measurements of the cross sections for the production of single top quarks and antiquarks in the t channel, and their ratio, are presented for proton-proton collisions at a center-of-mass energy of 13 TeV. The data set used was recorded in 2016 by the CMS detector at the LHC and corresponds to an integrated luminosity of 35.9 fb−1. Events with one muon or electron are selected, and different categories of jet and b jet multiplicity and multivariate discriminators are applied to separate the signal from the background. The cross sections for the t-channel production of single top quarks and antiquarks are measured to be 130±1(stat)±19(syst)pb and 77±1(stat)±12(syst)pb, respectively, and their ratio is 1.68±0.02(stat)±0.05(syst). The results are in agreement with the predictions from the standard model.

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Chadeeva, M., Philippov, D., Popova, E., Rusinov, V., Matveev, V., Dremin, I., Чадеева, Марина Валентиновна, Русинов, Владимир Юрьевич, Матвеев, Виктор Анатольевич

© 2020, CERN for the benefit of the CMS collaboration.A measurement is presented of electroweak (EW) production of a W boson in association with two jets in proton–proton collisions at s=13Te. The data sample was recorded by the CMS Collaboration at the LHC and corresponds to an integrated luminosity of 35.9fb-1. The measurement is performed for the ℓνjj final state (with ℓν indicating a lepton–neutrino pair, and j representing the quarks produced in the hard interaction) in a kinematic region defined by invariant mass mjj>120Ge and transverse momenta pTj>25Ge. The cross section of the process is measured in the electron and muon channels yielding σEW(Wjj)=6.23±0.12(stat)±0.61(syst)pb per channel, in agreement with leading-order standard model predictions. The additional hadronic activity of events in a signal-enriched region is studied, and the measurements are compared with predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. Limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are -2.3

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Bychkova, O., Chistov, R., Danilov, M., Polikarpov, S., Tarkovskii, E., Матвеев, Виктор Анатольевич, Чистов, Руслан Николаевич, Данилов, Михаил Владимирович, Поликарпов, Сергей Михайлович

© 2020, The Author(s).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. [Figure not available: see fulltext.]

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Chadeeva, M., Polikarpov, S., Popova, E., Rusinov, V., Dremin, I., Матвеев, Виктор Анатольевич, Чадеева, Марина Валентиновна, Поликарпов, Сергей Михайлович, Русинов, Владимир Юрьевич

© 2019 The Author(s)A search is presented for pairs of light pseudoscalar bosons, in the mass range from 4 to 15 GeV, produced from decays of the 125 GeV Higgs boson. The decay modes considered are final states that arise when one of the pseudoscalars decays to a pair of tau leptons, and the other one either into a pair of tau leptons or muons. The search is based on proton-proton collisions collected by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV that correspond to an integrated luminosity of 35.9 fb−1. The 2μ2τ and 4τ channels are used in combination to constrain the product of the Higgs boson production cross section and the branching fraction into 4τ final state, σB, exploiting the linear dependence of the fermionic coupling strength of pseudoscalar bosons on the fermion mass. No significant excess is observed beyond the expectation from the standard model. The observed and expected upper limits at 95% confidence level on σB, relative to the standard model Higgs boson production cross section, are set respectively between 0.022 and 0.23 and between 0.027 and 0.19 in the mass range probed by the analysis.

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Bychkova, O., Chistov, R., Danilov, M., Polikarpov, S., Tarkovskii, E., Матвеев, Виктор Анатольевич, Чистов, Руслан Николаевич, Данилов, Михаил Владимирович, Поликарпов, Сергей Михайлович

© 2020, The Author(s).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. [Figure not available: see fulltext.].

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Chistov, R., Danilov, M., Polikarpov, S., Tarkovskii, E., Матвеев, Виктор Анатольевич, Чистов, Руслан Николаевич, Данилов, Михаил Владимирович, Поликарпов, Сергей Михайлович

© 2020 The Author(s)The transverse momentum (pT) spectra of inclusively produced Λc + baryons are measured via the exclusive decay channel Λc +→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 Λc + rapidity interval |y|<1 in the pT range of 5–20GeV/c in pp and 10–20GeV/c in PbPb collisions. The observed yields of Λc + for pT of 10–20GeV/c suggest a suppression in central PbPb collisions compared to pp collisions scaled by the number of nucleon-nucleon (NN) interactions. The Λc +/D0 production 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 pT range.

2020, Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Matveev, V., Bychkova, O., Chistov, R., Danilov, M., Polikarpov, S., Tarkovskii, E., Матвеев, Виктор Анатольевич, Чистов, Руслан Николаевич, Данилов, Михаил Владимирович, Поликарпов, Сергей Михайлович

© 2019, CERN for the benefit of the CMS collaboration.Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of proton–proton collisions at a center-of-mass energy of 13Te, collected by the CMS experiment at the LHC in 2016–2018 and corresponding to an integrated luminosity of 137fb-1. The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable MT 2 for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving R-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.