Publications
1150 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of the inclusive and differential Higgs boson production cross sections in the leptonic WW decay mode at p root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-48, ISSN: 1029-8479
Measurements of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at s√ = 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016–2018, corresponding to an integrated luminosity of 137 fb−1. Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jet multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86.5 ± 9.5 fb, consistent with the Standard Model expectation of 82.5 ± 4.2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 813, Pages: 1-25, ISSN: 0370-2693
Measurements of the second Fourier harmonic coefficient (v2) of the azimuthal distributions of promptand nonprompt D0 mesons produced in pp and pPb collisions are presented. Nonprompt D0 mesons comefrom beauty hadron decays. The data samples are collected by the CMS experiment at nucleon-nucleoncenter-of-mass energies of 13 and 8.16 TeV, respectively. In high multiplicity pp collisions, v2 signalsfor prompt charm hadrons are reported for the first time, and are found to be comparable to those forlight-flavor hadron species over a transverse momentum (pT) range of 2–6 GeV. Compared at similarevent multiplicities, the prompt D0 meson v2 values in pp and pPb collisions are similar in magnitude.The v2 values for open beauty hadrons are extracted for the first time via nonprompt D0 mesons inpPb collisions. For pT in the range of 2–5 GeV, the results suggest that v2 for nonprompt D0 mesons issmaller than that for prompt D0 mesons. These new measurements indicate a positive charm hadron v2in pp collisions and suggest a mass dependence in v2 between charm and beauty hadrons in the pPbsystem. These results provide insights into the origin of heavy-flavor quark collectivity in small systems
Khachatryan V, Sirunyan AM, Tumasyan A, et al., 2021, The very forward CASTOR calorimeter of the CMS experiment, Journal of Instrumentation, Vol: 16, Pages: 1-65, ISSN: 1748-0221
The physics motivation, detector design, triggers, calibration, alignment, simulation, and overall performance of the very forward CASTOR calorimeter of the CMS experiment are reviewed. The CASTOR Cherenkov sampling calorimeter is located very close to the LHC beam line, at a radial distance of about 1cm from the beam pipe, and at 14.4m from the CMS interaction point, covering the pseudorapidity range of −6.6 < η < −5.2. It was designed to withstand high ambient radiation and strong magnetic fields. The performance of the detector in measurements of forward energy density, jets, and processes characterized by rapidity gaps, is reviewed using data collected in proton and nuclear collisions at the LHC.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for the lepton flavor violating decay tau -> 3 mu in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-37, ISSN: 1029-8479
Results are reported from a search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at s√ = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb−1 recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction ℬ(τ → 3μ) of 8.0 × 10−8 at 90% confidence level is obtained, with an expected upper limit of 6.9 × 10−8.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Evidence for Higgs boson decay to a pair of muons, The Journal of High Energy Physics, Vol: 2021, ISSN: 1029-8479
Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at s√ = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at s√ = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb−1, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is 1.19+0.40−0.39(stat)+0.15−0.14(syst). This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in pPb collisions at root s(NN)=8.16 TeV, Physical Review C: Nuclear Physics, Vol: 103, Pages: 1-17, ISSN: 0556-2813
Event-by-event long-range correlations of azimuthal anisotropy Fourier coefficients (vn) in 8.16 TeV pPb data, collected by the CMS experiment at the CERN Large Hadron Collider, are extracted using a subevent four-particle cumulant technique applied to very low multiplicity events. Each combination of four charged particles is selected from either two, three, or four distinct subevent regions of a pseudorapidity range from −2.4 to 2.4 of the CMS tracker, and with transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant technique, correlations between vn of different orders are measured as functions of particle multiplicity and compared to the standard cumulant method without subevents over a wide event multiplicity range. At high multiplicities, the v2 and v3 coefficients exhibit an anticorrelation; this behavior is observed consistently using various methods. The v2 and v4 correlation strength is found to depend on the number of subevents used in the calculation. As the event multiplicity decreases, the results from different subevent methods diverge because of different contributions of noncollective or few-particle correlations. Correlations extracted with the four-subevent method exhibit a tendency to diminish monotonically toward the lowest multiplicity region (about 20 charged tracks) investigated. These findings extend previous studies to a significantly lower event multiplicity range and establish the evidence for the onset of long-range collective multiparticle correlations in small system collisions.
Sirunyan AM, CMS Collaboration, Tumasyan A, et al., 2021, Search for dark matter produced in association with a leptonically decaying Z boson in proton-proton collisions at s = 13 Te ., European Physical Journal C: Particles and Fields, Vol: 81, Pages: 13-13, ISSN: 1124-1861
A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass energy of 13 Te , collected by the CMS experiment at the LHC in 2016-2018, corresponding to an integrated luminosity of 137 fb - 1 . The search uses the decay channels Z → e e and Z → μ μ . No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Evidence for electroweak production of four charged leptons and two jets in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 812, Pages: 1-25, ISSN: 0370-2693
Evidence is presented for the electroweak (EW) production of two jets (jj) in association with two Zbosons and constraints on anomalous quartic gauge couplings are set. The analysis is based on a data sample of proton-proton collisions at √s=13 TeV collected with the CMS detector in 2016–2018, and corresponding to an integrated luminosity of 137 fb−1. The search is performed in the fully leptonic final state ZZ→ ′ ′, where , ′=e, μ. The EW production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. The cross sections for the EW production are measured in three fiducial volumes and the result is σEW(pp→ZZjj→ ′ ′jj) =0.33+0.11−0.10(stat)+0.04−0.03(syst) fb in the most inclusive volume, in agreement with the standard model prediction of 0.275 ±0.021 fb. Measurements of total cross sections for jj production in association with two Z bosons are also reported. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0, T1, T2, T8, and T9.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for top squark pair production using dilepton final states in pp collision data collected at s√=13TeV, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-30, ISSN: 1124-1861
A search is presented for supersymmetric partners of the top quark (top squarks) in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from bquarks, and missing transverse momentum. The search uses data from proton-proton collisions at s√=13TeV collected with the CMS detector, corresponding to an integrated luminosity of 137fb−1. Hypothetical signal events are efficiently separated from the dominant top quark pair production background with requirements on the significance of the missing transverse momentum and on transverse mass variables. No significant deviation is observed from the expected background. Exclusion limits are set in the context of simplified supersymmetric models with pair-produced lightest top squarks. For top squarks decaying exclusively to a top quark and a lightest neutralino, lower limits are placed at 95% confidence level on the masses of the top squark and the neutralino up to 925 and 450GeV, respectively. If the decay proceeds via an intermediate chargino, the corresponding lower limits on the mass of the lightest top squark are set up to 850GeV for neutralino masses below 420GeV. For top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1.4TeV and 900GeV respectively for the top squark and the lightest neutralino.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at s=13 TeV, Physics Letters B, Vol: 812, Pages: 1-27, ISSN: 0370-2693
The first measurements of production cross sections of polarized same-sign W±W±boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W±scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fb is set on the production cross section for longitudinally polarized same-sign W±W±boson pairs. The electroweak production of same-sign W±W±boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Dependence of inclusive jet production on the anti-k(T) distance parameter in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-43, ISSN: 1029-8479
The dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter R of the anti-kT algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb−1 collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum pT and rapidity y, for R in the range 0.1 to 1.2 to those using R = 0.4 are presented in the region 84 < pT < 1588 GeV and |y| < 2.0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with R is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Inclusive search for highly boosted Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at s√ = 13 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-49, ISSN: 1029-8479
A search for standard model Higgs bosons (H) produced with transverse momentum (pT) greater than 450 GeV and decaying to bottom quark-antiquark pairs (bb¯¯¯) is performed using proton-proton collision data collected by the CMS experiment at the LHC at s√ = 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb−1. The search is inclusive in the Higgs boson production mode. Highly Lorentz-boosted Higgs bosons decaying to bb¯¯¯ are reconstructed as single large-radius jets, and are identified using jet substructure and a dedicated b tagging technique based on a deep neural network. The method is validated with Z → bb¯¯¯ decays. For a Higgs boson mass of 125 GeV, an excess of events above the background assuming no Higgs boson production is observed with a local significance of 2.5 standard deviations (σ), while the expectation is 0.7. The corresponding signal strength and local significance with respect to the standard model expectation are μH = 3.7 ± 1.2(stat)+0.8−0.7(syst)+0.8−0.5(theo) and 1.9 σ. Additionally, an unfolded differential cross section as a function of Higgs boson pT for the gluon fusion production mode is presented, assuming the other production modes occur at the expected rates.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of electroweak production of W gamma with two jets in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 811, Pages: 1-27, ISSN: 0370-2693
A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak Wγjj production in a restricted fiducial region is measured as 20.4 ±4.5fband the total cross section for Wγproduction in association with 2 jets in the same fiducial region is 108 ±16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for bottom-type, vectorlike quark pair production in a fully hadronic final state in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 112004 – 1-112004 – 30, ISSN: 1550-2368
A search is described for the production of a pair of bottom-type vectorlike quarks (VLQs), each decaying into a b or ¯b quark and either a Higgs or a Z boson, with a mass greater than 1000 GeV. The analysis is based on data from proton-proton collisions at a 13 TeV center-of-mass energy recorded at the CERN LHC, corresponding to a total integrated luminosity of 137 fb−1. As the predominant decay modes of the Higgs and Z bosons are to a pair of quarks, the analysis focuses on final states consisting of jets resulting from the six quarks produced in the events. Since the two jets produced in the decay of a highly Lorentz-boosted Higgs or Z boson can merge to form a single jet, nine independent analyses are performed, categorized by the number of observed jets and the reconstructed event mode. No signal in excess of the expected background is observed. Lower limits are set on the VLQ mass at 95% confidence level equal to 1570 GeV in the case where the VLQ decays exclusively to a b quark and a Higgs boson, 1390 GeV for when it decays exclusively to a b quark and a Z boson, and 1450 GeV for when it decays equally in these two modes. These limits represent significant improvements over the previously published VLQ limits.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the top quark Yukawa coupling from t(t)over-bar kinematic distributions in the dilepton final state in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-29, ISSN: 1550-2368
A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at √s=13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded with the CMS detector. The coupling strength with respect to the standard model value, Yt, is determined from kinematic distributions in t¯t final states containing ee, μμ, or eμ pairs. Variations of the Yukawa coupling strength lead to modified distributions for t¯t production. In particular, the distributions of the mass of the t¯t system and the rapidity difference of the top quark and antiquark are sensitive to the value of Yt. The measurement yields a best fit value of Yt=1.16+0.24−0.35, bounding Yt<1.54 at a 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurements of the W boson rapidity, helicity, double-differential cross sections, and charge asymmetry in pp collisions at root s=13 TeV, PHYSICAL REVIEW D, Vol: 102, Pages: 1-50, ISSN: 2470-0010
The differential cross section and charge asymmetry for inclusive W boson production at √s=13 TeV is measured for the two transverse polarization states as a function of the W boson absolute rapidity. The measurement uses events in which a W boson decays to a neutrino and either a muon or an electron. The data sample of proton-proton collisions recorded with the CMS detector at the LHC in 2016 corresponds to an integrated luminosity of 35.9 fb−1. The differential cross section and its value normalized to the total inclusive W boson production cross section are measured over the rapidity range |yW|<2.5. In addition to the total fiducial cross section, the W boson double-differential cross section, d2σ/dpℓTd|ηℓ|, and the charge asymmetry are measured as functions of the charged lepton transverse momentum and pseudorapidity. The precision of these measurements is used to constrain the parton distribution functions of the proton using the next-to-leading order NNPDF3.0 set.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Evidence for top quark production in nucleus-nucleus collisions, Physical Review Letters, Vol: 125, Pages: 222001-222001, ISSN: 0031-9007
Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10^{-6} sec, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon center-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production (σ_{tt[over ¯]}) via the selection of charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, σ_{tt[over ¯]}=2.54_{-0.74}^{+0.84} and 2.03_{-0.64}^{+0.71} μb, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of B-c(2S)(+) and B-c*(2S)(+) cross section ratios in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 092007 – 1-092007 – 21, ISSN: 1550-2368
The ratios of the Bc(2S)+ to B+c, B∗c(2S)+ to B+c, and B∗c(2S)+ to Bc(2S)+ production cross sections are measured in proton-proton collisions at √s=13 TeV, using a data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 143 fb−1. The three measurements are made in the B+c meson phase space region defined by the transverse momentum pT>15 GeV and absolute rapidity |y|<2.4, with the excited B(*)c(2S)+ states reconstructed through the B(*)+cπ+π−, followed by the B+c→J/ψπ+ and J/ψ→μ+μ− decays. The Bc(2S)+ to B+c, B∗c(2S)+ to B+c, and B∗c(2S)+ to Bc(2S)+ cross section ratios, including the unknown B(*)c(2S)+→B(*)+cπ+π− branching fractions, are (3.47±0.63(stat)±0.33(syst))%, (4.69±0.71(stat)±0.56(syst))%, and 1.35±0.32(stat)±0.09(syst), respectively. None of these ratios shows a significant dependence on the pT or |y| of the B+c meson. The normalized dipion invariant mass distributions from the decays B(*)c(2S)+→B(*)+cπ+π− are also reported.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for decays of the 125 GeV Higgs boson into a Z boson and a rho or phi meson, The Journal of High Energy Physics, Vol: 2020, Pages: 1-42, ISSN: 1029-8479
Decays of the 125 GeV Higgs boson into a Z boson and a ρ0(770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at s√ = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb−1. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740–940 and 730–950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, W+ W- boson pair production in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 092001 – 1-092001 – 30, ISSN: 1550-2368
A measurement of the W+W− boson pair production cross section in proton-proton collisions at √s=13 TeV is presented. The data used in this study are collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 35.9 fb−1. The W+W− candidate events are selected by requiring two oppositely charged leptons (electrons or muons). Two methods for reducing background contributions are employed. In the first one, a sequence of requirements on kinematic quantities is applied allowing a measurement of the total production cross section, 117.6±6.8 pb, which agrees well with the theoretical prediction. Fiducial cross sections are also reported for events with zero or one jet, and the change in the zero-jet fiducial cross section with the jet transverse momentum threshold is measured. Normalized differential cross sections are reported within the fiducial region. A second method for suppressing background contributions employs two random forest classifiers. The analysis based on this method includes a measurement of the total production cross section and also a measurement of the normalized jet multiplicity distribution in W+W− events. Finally, a dilepton invariant mass distribution is used to probe for physics beyond the standard model in the context of an effective field theory, and constraints on the presence of dimension-6 operators are derived.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Investigation into the event-activity dependence of gamma(nS) relative production in proton-proton collisions at root s=7 TeV, The Journal of High Energy Physics, Vol: 2020, Pages: 1-39, ISSN: 1029-8479
The ratios of the production cross sections between the excited ϒ(2S) and ϒ(3S) mesons and the ϒ(1S) ground state, detected via their decay into two muons, are studied as a function of the number of charged particles in the event. The data are from proton-proton collisions at s√ = 7 TeV, corresponding to an integrated luminosity of 4.8 fb−1, collected with the CMS detector at the LHC. Evidence of a decrease in these ratios as a function of the particle multiplicity is observed, more pronounced at low transverse momentum pμμT. For ϒ(nS) mesons with pμμT > 7 GeV, where most of the data were collected, the correlation with multiplicity is studied as a function of the underlying event transverse sphericity and the number of particles in a cone around the ϒ(nS) direction. The ratios are found to be multiplicity independent for jet-like events. The mean pμμT values for the ϒ(nS) states as a function of particle multiplicity are also measured and found to grow more steeply as their mass increases.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 809, Pages: 1-29, ISSN: 0370-2693
Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at √s=13 TeV at the LHC are reported. The data sample corresponds to an integrated luminosity of 137 fb−1, collected with the CMS detector during 2016–2018. The measurements are performed in the leptonic decay modes W±Z→ ±ν ′± ′∓and W±W±→ ±ν ′±ν, where , ′=e, μ. Differential fiducial cross sections as functions of the invariant masses of the jet and charged lepton pairs, as well as of the leading-lepton transverse momentum, are measured for W±W±production and are consistent with the standard model predictions. The dependence of differential cross sections on the invariant mass of the jet pair is also measured for WZ production. An observation of electroweak production of WZ boson pairs is reported with an observed (expected) significance of 6.8 (5.3) standard deviations. Constraints are obtained on the structure of quartic vector boson interactions in the framework of effective field theory.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of the B_{s}^{0}→X(3872)ϕ Decay., Physical Review Letters, Vol: 125, Pages: 152001-152001, ISSN: 0031-9007
Using a data sample of proton-proton collisions at sqrt[s]=13 TeV, corresponding to an integrated luminosity of 140 fb^{-1} collected by the CMS experiment in 2016-2018, the B_{s}^{0}→X(3872)ϕ decay is observed. Decays into J/ψπ^{+}π^{-} and K^{+}K^{-} are used to reconstruct, respectively, the X(3872) and ϕ. The ratio of the product of branching fractions B[B_{s}^{0}→X(3872)ϕ]B[X(3872)→J/ψπ^{+}π^{-}] to the product B[B_{s}^{0}→ψ(2S)ϕ]B[ψ(2S)→J/ψπ^{+}π^{-}] is measured to be [2.21±0.29(stat)±0.17(syst)]%. The ratio B[B_{s}^{0}→X(3872)ϕ]/B[B^{0}→X(3872)K^{0}] is found to be consistent with one, while the ratio B[B_{s}^{0}→X(3872)ϕ]/B[B^{+}→X(3872)K^{+}] is two times smaller. This suggests a difference in the production dynamics of the X(3872) in B^{0} and B_{s}^{0} meson decays compared to B^{+}. The reported observation may shed new light on the nature of the X(3872) particle.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of the B-s(0) -> X(3872)phi decay, Physical Review Letters, Vol: 125, Pages: 152001 – 1-152001 – 18, ISSN: 0031-9007
Using a data sample of proton-proton collisions at √s=13 TeV, corresponding to an integrated luminosity of 140 fb−1 collected by the CMS experiment in 2016–2018, the B0s→X(3872)ϕ decay is observed. Decays into J/ψπ+π− and K+K− are used to reconstruct, respectively, the X(3872) and ϕ. The ratio of the product of branching fractions B[B0s→X(3872)ϕ]B[X(3872)→J/ψπ+π−] to the product B[B0s→ψ(2S)ϕ]B[ψ(2S)→J/ψπ+π−] is measured to be [2.21±0.29(stat)±0.17(syst)]%. The ratio B[B0s→X(3872)ϕ]/B[B0→X(3872)K0] is found to be consistent with one, while the ratio B[B0s→X(3872)ϕ]/B[B+→X(3872)K+] is two times smaller. This suggests a difference in the production dynamics of the X(3872) in B0 and B0s meson decays compared to B+. The reported observation may shed new light on the nature of the X(3872) particle.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Observation of the production of three massive gauge bosons at root s=13 TeV, Physical Review Letters, Vol: 125, Pages: 151802 – 1-151802 – 18, ISSN: 0031-9007
The first observation is reported of the combined production of three massive gauge bosons (VVV with V=W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis is based on a data sample recorded by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 137 fb−1. The searches for individual WWW, WWZ, WZZ, and ZZZ production are performed in final states with three, four, five, and six leptons (electrons or muons), or with two same-sign leptons plus one or two jets. The observed (expected) significance of the combined VVV production signal is 5.7 (5.9) standard deviations and the corresponding measured cross section relative to the standard model prediction is 1.02+0.26−0.23. The significances of the individual WWW and WWZ production are 3.3 and 3.4 standard deviations, respectively. Measured production cross sections for the individual triboson processes are also reported.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for a light charged Higgs boson in the H-+/- -> cs channel in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, ISSN: 1550-2368
A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and a strange quark. The data sample was recorded in proton-proton collisions at √s=13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb−1. The search is performed in the process of top quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the final state comprises an isolated lepton, missing transverse momentum, and at least four jets, of which two are tagged as b jets. To enhance the search sensitivity, one of the jets originating from the charged Higgs boson is required to satisfy a charm tagging selection. No significant excess beyond standard model predictions is found in the dijet invariant mass distribution. An upper limit in the range 1.68%–0.25% is set on the branching fraction of the top quark decay to the charged Higgs boson and bottom quark for a charged Higgs boson mass between 80 and 160 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Reconstruction of signal amplitudes in the CMS electromagnetic calorimeter in the presence of overlapping proton-proton interactions, Journal of Instrumentation, Vol: 15, Pages: 1-45, ISSN: 1748-0221
A template fitting technique for reconstructing the amplitude of signals produced by the lead tungstate crystals of the CMS electromagnetic calorimeter is described. This novel approach is designed to suppress the contribution to the signal of the increased number of out-of-time interactions per beam crossing following the reduction of the accelerator bunch spacing from 50 to 25 ns at the start of Run 2 of the LHC. Execution of the algorithm is sufficiently fast for it to be employed in the CMS high-level trigger. It is also used in the offline event reconstruction. Results obtained from simulations and from Run 2 collision data (2015–2018) demonstrate a substantial improvement in the energy resolution of the calorimeter over a range of energies extending from a few GeV to several tens of GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Performance of the CMS Level-1 trigger in proton-proton collisions at root s=13 TeV, Journal of Instrumentation, Vol: 15, Pages: 1-61, ISSN: 1748-0221
At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13\TeV. During Run 2 (years 2015–2018) the LHC eventually reached a luminosity of 2.1× 1034 cm-2s-1, almost three times that reached during Run 1 (2009–2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016–2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Search for supersymmetry in proton-proton collisions at s√ = 13 TeV in events with high-momentum Z bosons and missing transverse momentum, The Journal of High Energy Physics, Vol: 2020, Pages: 1-42, ISSN: 1029-8479
A search for new physics in events with two highly Lorentz-boosted Z bosons and large missing transverse momentum is presented. The analyzed proton-proton collision data, corresponding to an integrated luminosity of 137 fb−1, were recorded at s√ = 13 TeV by the CMS experiment at the CERN LHC. The search utilizes the substructure of jets with large radius to identify quark pairs from Z boson decays. Backgrounds from standard model processes are suppressed by requirements on the jet mass and the missing transverse momentum. No significant excess in the event yield is observed beyond the number of background events expected from the standard model. For a simplified supersymmetric model in which the Z bosons arise from the decay of gluinos, an exclusion limit of 1920 GeV on the gluino mass is set at 95% confidence level. This is the first search for beyond-standard-model production of pairs of boosted Z bosons plus large missing transverse momentum.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Measurement of the Y(1S) pair production cross section and search for resonances decaying to Y(1S)mu(+)mu(-) in proton-proton collisions at root s=13 TeV, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 808, Pages: 1-27, ISSN: 0370-2693
The fiducial cross section for Y(1S)pair production in proton-proton collisions at a center-of-mass energy of 13 TeV in the region where both Y(1S)mesons have an absolute rapidity below 2.0 is measured to be 79 ±11 (stat)±6 (syst)±3 (B)pb assuming the mesons are produced unpolarized. The last uncertainty corresponds to the uncertainty in the Y(1S)meson dimuon branching fraction. The measurement is performed in the final state with four muons using proton-proton collision data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb−1. This process serves as a standard model reference in a search for narrow resonances decaying to Y(1S)μ+μ−in the same final state. Such a resonance could indicate the existence of a tetraquark that is a bound state of two bquarks and two ̄bantiquarks. The tetraquark search is performed for masses in the vicinity of four times the bottom quark mass, between 17.5 and 19.5 GeV, while a generic search for other resonances is performed for masses between 16.5 and 27 GeV. No significant excess of events compatible with a narrow resonance is observed in the data. Limits on the production cross section times branching fraction to four muons via an intermediate Y(1S)resonance are set as a function of the resonance mass.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.