Publications
1759 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurement of single-diffractive dijet production in proton-proton collisions at s = 8 Te with the CMS and TOTEM experiments., Eur Phys J C Part Fields, Vol: 80, Pages: 1164-1164, ISSN: 1434-6044
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss ξ and the four-momentum transfer squared t. Both processes p p → p X and p p → X p , i.e. with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at s√=8TeV during a dedicated run with β∗=90m at low instantaneous luminosity and correspond to an integrated luminosity of 37.5nb−1. The single-diffractive dijet cross section σ p X jj, in the kinematic region ξ<0.1, 0.03<|t|<1GeV2, with at least two jets with transverse momentum pT>40GeV, and pseudorapidity |η|<4.4, is 21.7±0.9(stat)+3.0−3.3(syst)±0.9(lumi)nb. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of ξ, is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range −2.9≤log10x≤−1.6, is R=(σ p X jj/Δξ)/σjj=0.025±0.001(stat)±0.003(syst), where σ p X jj and σjj are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for a heavy resonance decaying to a top quark and a W boson at root s=13 TeV in the fully hadronic final state, The Journal of High Energy Physics, Vol: 2021, Pages: 1-46, ISSN: 1029-8479
A search for a heavy resonance decaying to a top quark and a W boson in the fully hadronic final state is presented. The analysis is performed using data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb−1 recorded by the CMS experiment at the LHC. The search is focused on heavy resonances, where the decay products of each top quark or W boson are expected to be reconstructed as a single, large-radius jet with a distinct substructure. The production of an excited bottom quark, b*, is used as a benchmark when setting limits on the cross section for a heavy resonance decaying to a top quark and a W boson. The hypotheses of b* quarks with left-handed, right-handed, and vector-like chiralities are excluded at 95% confidence level for masses below 2.6, 2.8, and 3.1 TeV, respectively. These are the most stringent limits on the b* quark mass to date, extending the previous best limits by almost a factor of two.
Tonon N, Petersen HA, Martin MA, et al., 2021, Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-55, ISSN: 1029-8479
A search for new top quark interactions is performed within the framework of an effective field theory using the associated production of either one or two top quarks with a Z boson in multilepton final states. The data sample corresponds to an integrated luminosity of 138 fb−1 of proton-proton collisions at s√ = 13 TeV collected by the CMS experiment at the LHC. Five dimension-six operators modifying the electroweak interactions of the top quark are considered. Novel machine-learning techniques are used to enhance the sensitivity to effects arising from these operators. Distributions used for the signal extraction are parameterized in terms of Wilson coefficients describing the interaction strengths of the operators. All five Wilson coefficients are simultaneously fit to data and 95% confidence level intervals are computed. All results are consistent with the SM expectations
Tumasyan A, Adam W, Ambrogi F, et al., 2021, Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-48, ISSN: 1029-8479
The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13 TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb−1. The differential production cross sections of the D∗±, D±, and D0 (D¯¯¯¯0) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < pT < 100 GeV and |η| < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-72, ISSN: 1029-8479
A search is presented for new particles produced at the LHC in proton-proton collisions at s√ = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb−1, collected in 2017–2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb−1, collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Observation of tW production in the single-lepton channel in pp collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 32, ISSN: 1029-8479
A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at s√ = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb−1 collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant tt¯ background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 ± 4 (stat) ± 12 (syst) pb, consistent with the standard model.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Search for a heavy Higgs boson decaying into two lighter Higgs bosons in the tau tau bb final state at 13TeV, The Journal of High Energy Physics, Vol: 2021, Pages: 1-54, ISSN: 1029-8479
A search for a heavy Higgs boson H decaying into the observed Higgs boson h with a mass of 125 GeV and another Higgs boson hS is presented. The h and hS bosons are required to decay into a pair of tau leptons and a pair of b quarks, respectively. The search uses a sample of 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. Mass ranges of 240–3000 GeV for mH and 60–2800 GeV for mhS are explored in the search. No signal has been observed. Model independent 95% confidence level upper limits on the product of the production cross section and the branching fractions of the signal process are set with a sensitivity ranging from 125 fb (for mH = 240 GeV) to 2.7 fb (for mH = 1000 GeV). These limits are compared to maximally allowed products of the production cross section and the branching fractions of the signal process in the next-to-minimal supersymmetric extension of the standard model.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurements of the electroweak diboson production cross sections in proton-proton collisions at sqrt[s]=5.02 TeV using leptonic decays, Physical Review Letters, Vol: 127, ISSN: 0031-9007
The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb^{-1}. Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as σ_{WW}=37.0_{-5.2}^{+5.5}(stat)_{-2.6}^{+2.7}(syst) pb, σ_{WZ}=6.4_{-2.1}^{+2.5}(stat)_{-0.3}^{+0.5}(syst) pb, and σ_{ZZ}=5.3_{-2.1}^{+2.5}(stat)_{-0.4}^{+0.5}(syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurement of differential t(t)over-bar production cross sections in the full kinematic range using lepton plus jets events from proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-93, ISSN: 1550-2368
Measurements of differential and double-differential cross sections of top-quark pair (t¯t) production are presented in the lepton+jets channels with a single electron or muon and jets in the final state. The analysis combines for the first time signatures of top quarks with low transverse momentum pT, where the top-quark decay products can be identified as separated jets and isolated leptons, and with high pT, where the decay products are collimated and overlap. The measurements are based on proton-proton collision data at √s=13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 137 fb−1. The cross sections are presented at the parton and particle levels, where the latter minimizes extrapolations based on theoretical assumptions. Most of the measured differential cross sections are well described by standard model predictions with the exception of some double-differential distributions. The inclusive t¯t production cross section is measured to be σt¯t=791±25 pb, which constitutes the most precise measurement in the lepton+jets channel to date.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-35, ISSN: 1124-1861
A combination of searches for top squark pairproduction using proton–proton collision data at a centerof-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb−1 collected by theCMS experiment, is presented. Signatures with at least 2jets and large missing transverse momentum are categorizedinto events with 0, 1, or 2 leptons. New results for regionsof parameter space where the kinematical properties of topsquark pair production and top quark pair production are verysimilar are presented. Depending on the model, the combinedresult excludes a top squark mass up to 1325 GeV for a massless neutralino, and a neutralino mass up to 700 GeV for a topsquark mass of 1150 GeV. Top squarks with masses from 145to 295 GeV, for neutralino masses from 0 to 100 GeV, witha mass difference between the top squark and the neutralinoin a window of 30 GeV around the mass of the top quark,are excluded for the first time with CMS data. The resultsof theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator inassociation with a top quark pair. Upper limits are set on thecross section for mediator particle masses of up to 420 GeV
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Study of Z boson plus jets events using variables sensitive to double-parton scattering in pp collisions at 13 TeV, The Journal of High Energy Physics, Vol: 176, Pages: 1-23, ISSN: 1029-8479
Double-parton scattering is investigated using events with a Z boson and jets.The Z boson is reconstructed using only the dimuon channel. The measurements are performed with proton-proton collision data recorded by the CMS experiment at the LHCat √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1collected in theyear 2016. Differential cross sections of Z+ ≥1 jet and Z+ ≥2 jets are measured withtransverse momentum of the jets above 20 GeV and pseudorapidity |η| < 2.4. Several distributions with sensitivity to double-parton scattering effects are measured as functions ofthe angle and the transverse momentum imbalance between the Z boson and the jets. Themeasured distributions are compared with predictions from several event generators withdifferent hadronization models and different parameter settings for multiparton interactions. The measured distributions show a dependence on the hadronization and multiparton interaction simulation parameters, and are important input for future improvementsof the simulations.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurements of the pp -> W-+/-gamma gamma and pp -> Z gamma gamma cross sections at root s=13 TeV and limits on anomalous quartic gauge couplings, The Journal of High Energy Physics, Vol: 174, ISSN: 1029-8479
The cross section for W or Z boson production in association with two photonsis measured in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data setcorresponds to an integrated luminosity of 137 fb−1collected by the CMS experiment atthe LHC. The W → `ν and Z → `` decay modes (where ` = e, µ) are used to extract theWγγ and Zγγ cross sections in a phase space defined by electron (muon) with transversemomentum larger than 30 GeV and photon transverse momentum larger than 20 GeV.All leptons and photons are required to have absolute pseudorapidity smaller than 2.5.The measured cross sections in this phase space are σ(Wγγ) = 13.6+1.9−1.9(stat)+4.0−4.0(syst) ±0.08 (PDF + scale)fb and σ(Zγγ) = 5.41+0.58−0.55 (stat)+0.64−0.70 (syst) ± 0.06 (PDF + scale)fb.Limits on anomalous quartic gauge couplings are set in the framework of an effectivefield theory with dimension-8 operators.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Search for chargino-neutralino production in events with Higgs and W bosons using 137 fb(-1) of proton-proton collisions at root s=13 TeV, The Journal of High Energy Physics, Vol: 45, Pages: 1-46, ISSN: 1029-8479
A search for electroweak production of supersymmetric (SUSY) particles in final states with one lepton, a Higgs boson decaying to a pair of bottom quarks, and large missing transverse momentum is presented. The search uses data from proton-proton collisions at a center-of-mass energy of 13 TeV collected using the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. The observed yields are consistent with backgrounds expected from the standard model. The results are interpreted in the context of a simplified SUSY model of chargino-neutralino production, with the chargino decaying to a W boson and the lightest SUSY particle (LSP) and the neutralino decaying to a Higgs boson and the LSP. Charginos and neutralinos with masses up to 820 GeV are excluded at 95% confidence level when the LSP mass is small, and LSPs with mass up to 350 GeV are excluded when the masses of the chargino and neutralino are approximately 700 GeV.
Tumasyan A, Adam W, Andrejkovic JW, et al., 2021, Measurement of the electroweak production of Z gamma and two jets in proton-proton collisions at root s=13 TeV and constraints on anomalous quartic gauge couplings, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-29, ISSN: 1550-2368
The first observation of the electroweak (EW) production of a Z boson, a photon, and two forward jets (Zγjj) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. A data set corresponding to an integrated luminosity of 137 fb−1, collected by the CMS experiment at the LHC in 2016–2018 is used. The measured fiducial cross section for EW Zγjj is σEW=5.21±0.52(stat)±0.56(syst) fb=5.21±0.76 fb. Single-differential cross sections in photon, leading lepton, and leading jet transverse momenta, and double-differential cross sections in mjj and |Δηjj| are also measured. Exclusion limits on anomalous quartic gauge couplings are derived at 95% confidence level in terms of the effective field theory operators M0 to M5, M7, T0 to T2, and T5 to T9.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at root s=13 Te V, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-29, ISSN: 1550-2368
A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV. The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb−1. This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm, each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of R-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Observation of forward neutron multiplicity dependence of dimuon acoplanarity in ultraperipheral Pb-Pb collisions at sqrt[s_{NN}]=5.02 TeV, Physical Review Letters, Vol: 127, ISSN: 0031-9007
The first measurement of the dependence of γγ→μ^{+}μ^{-} production on the multiplicity of neutrons emitted very close to the beam direction in ultraperipheral heavy ion collisions is reported. Data for lead-lead interactions at sqrt[s_{NN}]=5.02 TeV, with an integrated luminosity of approximately 1.5 nb^{-1}, are collected using the CMS detector at the LHC. The azimuthal correlations between the two muons in the invariant mass region 8<m_{μμ}<60 GeV are extracted for events including 0, 1, or at least 2 neutrons detected in the forward pseudorapidity range |η|>8.3. The back-to-back correlation structure from leading-order photon-photon scattering is found to be significantly broader for events with a larger number of emitted neutrons from each nucleus, corresponding to interactions with a smaller impact parameter. This observation provides a data-driven demonstration that the average transverse momentum of photons emitted from relativistic heavy ions has an impact parameter dependence. These results provide new constraints on models of photon-induced interactions in ultraperipheral collisions. They also provide a baseline to search for possible final-state effects on lepton pairs caused by traversing a quark-gluon plasma produced in hadronic heavy ion collisions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Constraints on anomalous Higgs boson couplings to vector bosons and fermions in its production and decay using the four-lepton final state, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-51, ISSN: 1550-2368
Studies of CP violation and anomalous couplings of the Higgs boson to vector bosons and fermions are presented. The data were acquired by the CMS experiment at the LHC and correspond to an integrated luminosity of 137 fb−1 at a proton-proton collision energy of 13 TeV. The kinematic effects in the Higgs boson’s four-lepton decay H→4ℓ and its production in association with two jets, a vector boson, or top quarks are analyzed, using a full detector simulation and matrix element techniques to identify the production mechanisms and to increase sensitivity to the tensor structure of the Higgs boson interactions. A simultaneous measurement is performed of up to five Higgs boson couplings to electroweak vector bosons (HVV), two couplings to gluons (Hgg), and two couplings to top quarks (Htt). The CP measurement in the Htt interaction is combined with the recent measurement in the H→γγ channel. The results are presented in the framework of anomalous couplings and are also interpreted in the framework of effective field theory, including the first study of CP properties of the Htt and effective Hgg couplings from a simultaneous analysis of the gluon fusion and top-associated processes. The results are consistent with the standard model of particle physics.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for W′ bosons decaying to a top and a bottom quark at s=13TeV in the hadronic final state, Physics Letters B, Vol: 820, Pages: 1-26, ISSN: 0370-2693
A search is performed for W bosons decaying to a top and a bottom quark in the all-hadronic final state,in proton-proton collisions at a center-of-mass energy of 13 TeV. The analyzed data were collected bythe CMS experiment between 2016 and 2018 and correspond to an integrated luminosity of 137 fb−1.Deep neural network algorithms are used to identify the jet initiated by the bottom quark and thejet containing the decay products of the top quark when the W boson from the top quark decayshadronically. No excess above the estimated standard model background is observed. Upper limits onthe production cross sections of W bosons decaying to a top and a bottom quark are set. Both left- andright-handed W bosons with masses below 3.4 TeV are excluded at 95% confidence level, and the moststringent limits to date on W bosons decaying to a top and a bottom quark in the all-hadronic final stateare obtained.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Search for top squark production in fully hadronic final states in proton-proton collisions at root s=13 TeV, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-46, ISSN: 1550-2368
A search for production of the supersymmetric partners of the top quark, top squarks, is presented. The search is based on proton-proton collision events containing multiple jets, no leptons, and large transverse momentum imbalance. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 137 fb−1. The targeted signal production scenarios are direct and gluino-mediated top squark production, including scenarios in which the top squark and neutralino masses are nearly degenerate. The search utilizes novel algorithms based on deep neural networks that identify hadronically decaying top quarks and W bosons, which are expected in many of the targeted signal models. No statistically significant excess of events is observed relative to the expectation from the standard model, and limits on the top squark production cross section are obtained in the context of simplified supersymmetric models for various production and decay modes. Exclusion limits as high as 1310 GeV are established at the 95% confidence level on the mass of the top squark for direct top squark production models, and as high as 2260 GeV on the mass of the gluino for gluino-mediated top squark production models. These results represent a significant improvement over the results of previous searches for supersymmetry by CMS in the same final state.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Precision luminosity measurement in proton–proton collisions at s√=13TeV in 2015 and 2016 at CMS, The European Physical Journal C, Vol: 81, Pages: 1-42, ISSN: 1434-6044
The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton–proton collisions at s√=13TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 fb−1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Constraints on the initial state of Pb-Pb collisions via measurements of Z-boson yields and azimuthal anisotropy at sqrt[s_{NN}]=5.02 TeV, Physical Review Letters, Vol: 127, ISSN: 0031-9007
The CMS experiment at the LHC has measured the differential cross sections of Z bosons decaying to pairs of leptons, as functions of transverse momentum and rapidity, in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measured Z boson elliptic azimuthal anisotropy coefficient is compatible with zero, showing that Z bosons do not experience significant final-state interactions in the medium produced in the collision. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, Measurements of angular distance and momentum ratio distributions in three-jet and Z plus two-jet final states in pp collisions, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-27, ISSN: 1124-1861
Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and Z + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and Z + two-jet events are based on data collected at a center-of-mass energy of 8TeV, corresponding to an integrated luminosity of 19.8fb−1. The Z + two-jet events are reconstructed in the dimuon decay channel of the Z boson. The three-jet measurement is extended to include s√=13TeV data corresponding to an integrated luminosity of 2.3fb−1. The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.
Sirunyan AM, Tumasyan A, Adam W, et al., 2021, First measurement of the cross section for top quark pair productionwith additional charm jets using dileptonic final states in pp collisionsat √s = 13 TeV, Physics Letters B, Vol: 820, Pages: 1-30, ISSN: 0370-2693
The first measurement of the inclusive cross section for top quark pairs (tt) produced in association withtwo additional charm jets is presented. The analysis uses the dileptonic final states of tt events producedin proton-proton collisions at a centre-of-mass energy of 13 TeV. The data correspond to an integratedluminosity of 41.5 fb−1, recorded by the CMS experiment at the LHC. A new charm jet identificationalgorithm provides input to a neural network that is trained to distinguish among tt events with twoadditional charm (ttcc), bottom (ttbb), and light-flavour or gluon (ttLL) jets. By means of a templatefitting procedure, the inclusive ttcc, ttbb, and ttLL cross sections are simultaneously measured, togetherwith their ratios to the inclusive tt + two jets cross section. This provides measurements of the ttcc andttbb cross sections of 10.1 ± 1.2 (stat) ± 1.4 (syst) pb and 4.54 ± 0.35 (stat) ± 0.56 (syst) pb, respectively,in the full phase space. The results are compared and found to be consistent with predictions from twodifferent matrix element generators with next-to-leading order accuracy in quantum chromodynamics,interfaced with a parton shower simulation.
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 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.
Abazov VM, Abbott B, Acharya BS, et al., 2021, Odderon Exchange from Elastic Scattering Differences between <i>pp</i> and <i>p(p)over-bar</i> Data at 1.96 TeV and from <i>pp</i> Forward Scattering Measurements, PHYSICAL REVIEW LETTERS, Vol: 127, ISSN: 0031-9007
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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 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.
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