Publications
1082 results found
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for long-lived particles decaying into displaced jets in proton-proton collisions at root s=13 TeV, Physical Review D, Vol: 99, ISSN: 2470-0010
A search for long-lived particles decaying into jets is presented. Data were collected with the CMS detector at the LHC from proton-proton collisions at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9 fb−1. The search examines the distinctive topology of displaced tracks and secondary vertices. The selected events are found to be consistent with standard model predictions. For a simplified model in which long-lived neutral particles are pair produced and decay to two jets, pair production cross sections larger than 0.2 fb are excluded at 95% confidence level for a long-lived particle mass larger than 1000 GeV and proper decay lengths between 3 and 130 mm. Several supersymmetry models with gauge-mediated supersymmetry breaking or R-parity violation, where pair-produced long-lived gluinos or top squarks decay to several final-state topologies containing displaced jets, are also tested. For these models, in the mass ranges above 200 GeV, gluino masses up to 2300–2400 GeV and top squark masses up to 1350–1600 GeV are excluded for proper decay lengths approximately between 10 and 100 mm. These are the most restrictive limits to date on these models.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for single production of vector-like quarks decaying to a top quark and a W boson in proton-proton collisions at TeV, European Physical Journal C: Particles and Fields, Vol: 79, ISSN: 1434-6044
A search is presented for the single production of vector-like quarks in proton–proton collisions at √=13TeV. The data, corresponding to an integrated luminosity of 35.9fb−1, were recorded with the CMS experiment at the LHC. The analysis focuses on the vector-like quark decay into a top quark and a W boson, with one muon or electron in the final state. The mass of the vector-like quark candidate is reconstructed from hadronic jets, the lepton, and the missing transverse momentum. Methods for the identification of b quarks and of highly Lorentz boosted hadronically decaying top quarks and W bosons are exploited in this search. No significant deviation from the standard model background expectation is observed. Exclusion limits at 95% confidence level are set on the product of the production cross section and branching fraction as a function of the vector-like quark mass, which range from 0.3 to 0.03pb for vector-like quark masses of 700 to 2000GeV. Mass exclusion limits up to 1660GeV are obtained, depending on the vector-like quark type, coupling, and decay width. These represent the most stringent exclusion limits for the single production of vector-like quarks in this channel.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Study of the underlying event in top quark pair production in pp collisions at 13 TeV, The European Physical Journal C - Particles and Fields, Vol: 79, ISSN: 1434-6044
Measurements of normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event in top quark and antiquark pair production are presented. The measurements are performed in proton-proton collisions at a center-of-mass energy of 13 TeV , and are based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 fb−1 . Events containing one electron, one muon, and two jets from the hadronization and fragmentation of b quarks are used. These measurements characterize, for the first time, properties of the underlying event in top quark pair production and show no deviation from the universality hypothesis at energy scales typically above twice the top quark mass.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for new particles decaying to a jet and an emerging jet, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search is performed for events consistent with the pair production of a new heavy particle that acts as a mediator between a dark sector and normal matter, and that decays to a light quark and a new fermion called a dark quark. The search is based on data corresponding to an integrated luminosity of 16.1 fb−1 from proton-proton collisions at √=13 TeV collected by the CMS experiment at the LHC in 2016. The dark quark is charged only under a new quantum-chromodynamics-like force, and forms an “emerging jet” via a parton shower, containing long-lived dark hadrons that give rise to displaced vertices when decaying to standard model hadrons. The data are consistent with the expectation from standard model processes. Limits are set at 95% confidence level excluding dark pion decay lengths between 5 and 225 mm for dark mediators with masses between 400 and 1250 GeV. Decay lengths smaller than 5 and greater than 225 mm are also excluded in the lower part of this mass range. The dependence of the limit on the dark pion mass is weak for masses between 1 and 10 GeV. This analysis is the first dedicated search for the pair production of a new particle that decays to a jet and an emerging jet.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for new physics in final states with a single photon and missing transverse momentum in proton-proton collisions at √=13TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search is conducted for new physics in final states containing a photon and missing transverse momentum in proton-proton collisions at √=13 TeV, using the data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb−1. No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and models containing extra spatial dimensions, and limits on new physics parameters are calculated at 95% confidence level. For the two simplified dark matter production models considered, the observed (expected) lower limits on the mediator masses are both 950 (1150) GeV for 1 GeV dark matter mass. For an effective electroweak-dark matter contact interaction, the observed (expected) lower limit on the suppression parameter Λ is 850 (950) GeV. Values of the effective Planck scale up to 2.85–2.90 TeV are excluded for between 3 and 6 extra spatial dimensions.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for rare decays of Z and Higgs bosons to J/ and a photon in proton-proton collisions at 13 TeV, European Physical Journal C: Particles and Fields, Vol: 79, ISSN: 1434-6044
A search is presented for decays of Z and Higgs bosons to a J/ meson and a photon, with the subsequent decay of the J/ to + −. The analysis uses data from proton-proton collisions with an integrated luminosity of 35.9fb−1 at √=13TeV collected with the CMS detector at the LHC. The observed limit on the Z→J/ decay branching fraction, assuming that the J/ meson is produced unpolarized, is 1.4×10−6 at 95% confidence level, which corresponds to a rate higher than expected in the standard model by a factor of 15. For extreme-polarization scenarios, the observed limit changes from −13.6 to +8.6% with respect to the unpolarized scenario. The observed upper limit on the branching fraction for H→J/ where the J/ meson is assumed to be transversely polarized is 7.6×10−4, a factor of 260 larger than the standard model prediction. The results for the Higgs boson are combined with previous data from proton-proton collisions at √=8TeV to produce an observed upper limit on the branching fraction for H→J/ that is a factor of 220 larger than the standard model value.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for the Higgs Boson decaying to two muons in proton-proton collisions at root s=13 TeV, Physical Review Letters, Vol: 122, ISSN: 0031-9007
A search for the Higgs boson decaying to two oppositely charged muons is presented using data recorded by the CMS experiment at the CERN LHC in 2016 at a center-of-mass energy √s=13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Data are found to be compatible with the predicted background. For a Higgs boson with a mass of 125.09 GeV, the 95% confidence level observed (background-only expected) upper limit on the production cross section times the branching fraction to a pair of muons is found to be 3.0 (2.5) times the standard model expectation. In combination with data recorded at center-of-mass energies √s=7 and 8 TeV, the background-only expected upper limit improves to 2.2 times the standard model value with a standard model expected significance of 1.0 standard deviation. The corresponding observed upper limit is 2.9 with an observed significance of 0.9 standard deviation. This corresponds to an observed upper limit on the standard model Higgs boson branching fraction to muons of 6.4×10−4 and to an observed signal strength of 1.0±1.0(stat)±0.1(syst).
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for supersymmetry in events with a photon, a lepton, and missing transverse momentum in proton-proton collisions at √<i>s</i>=13 TeV, Publisher: SPRINGER
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Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for dark matter particles produced in association with a top quark pair at root s=13 TeV, Physical Review Letters, Vol: 122, ISSN: 0031-9007
A search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at √s=13 TeV. The data correspond to an integrated luminosity of 35.9 fb−1 recorded by the CMS detector at the LHC. No significant excess over the standard model expectation is observed. The results are interpreted using simplified models of dark matter production via spin-0 mediators that couple to dark matter particles and to standard model quarks, providing constraints on the coupling strength between the mediator and the quarks. These are the most stringent collider limits to date for scalar mediators, and the most stringent for pseudoscalar mediators at low masses.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for Higgs boson pair production in the gamma gamma b(b)over-bar final state in pp collisions at root s=13 TeV, Physics Letters B, Vol: 788, Pages: 7-36, ISSN: 0370-2693
A search is presented for the production of a pair of Higgs bosons, where one decays into two photons and the other one into a bottom quark–antiquark pair. The analysis is performed using proton–proton collision data at recorded in 2016 by the CMS detector at the LHC, corresponding to an integrated luminosity of . The results are in agreement with standard model (SM) predictions. In a search for resonant production, upper limits are set on the cross section for new spin-0 or spin-2 particles. For the SM-like nonresonant production hypothesis, the data exclude a product of cross section and branching fraction larger than at 95% confidence level (CL), corresponding to about 24 times the SM prediction. Values of the effective Higgs boson self-coupling are constrained to be within the range at 95% CL, assuming all other Higgs boson couplings are at their SM value. The constraints on are the most restrictive to date.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for low-mass resonances decaying into bottom quark-antiquark pairs in proton-proton collisions at root s=13 TeV, Physical Review D, Vol: 99, ISSN: 2470-0010
A search for narrow, low-mass, scalar, and pseudoscalar resonances decaying to bottom quark-antiquark pairs is presented. The search is based on events recorded in √s=13 TeV proton-proton collisions with the CMS detector at the LHC, collected in 2016, and corresponding to an integrated luminosity of 35.9 fb−1. The search selects events in which the resonance would be produced with high transverse momentum because of the presence of initial- or final-state radiation. In such events, the decay products of the resonance would be reconstructed as a single large-radius jet with high mass and two-prong substructure. A potential signal would be identified as a narrow excess in the jet invariant mass spectrum. No evidence for such a resonance is observed within the mass range from 50 to 350 GeV, and upper limits at 95% confidence level are set on the product of the cross section and branching fraction to a bottom quark-antiquark pair. These constitute the first constraints from the LHC on exotic bottom quark-antiquark resonances with masses below 325 GeV.
Scandale W, Arduini G, Cerutti F, et al., 2019, Dechanneling of high energy particles in a long bent crystal, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, Vol: 438, Pages: 38-41, ISSN: 0168-583X
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for pair-produced three-jet resonances in proton-proton collisions at root s=13 TeV, Physical Review D, Vol: 99, ISSN: 2470-0010
A search has been performed for pair-produced resonances decaying into three jets. The proton-proton collision data used for this analysis were collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 35.9 fb−1. The mass range from 200 to 2000 GeV is explored in four separate mass regions. The observations show agreement with standard model expectations. The results are interpreted within the framework of R-parity violating SUSY, where pair-produced gluinos decay to a six quark final state. Gluino masses below 1500 GeV are excluded at 95% confidence level. An analysis based on data with multijet events reconstructed at the trigger level extends the reach to masses as low as 200 GeV. Improved analysis techniques have led to enhanced sensitivity, allowing the most stringent limits to date to be set on gluino pair production.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for heavy Majorana neutrinos in same-sign dilepton channels in proton-proton collisions at root s = TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search is performed for a heavy Majorana neutrino (N), produced in leptonic decay of a W boson propagator and decaying into a W boson and a lepton, with the CMS detector at the LHC. The signature used in this search consists of two same-sign leptons, in any flavor combination of electrons and muons, and at least one jet. The data were collected during 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The results are found to be consistent with the expected standard model background. Upper limits are set in the mass range between 20 and 1600 GeV in the context of a Type-I seesaw mechanism, on |VeN|2, |VμN|2, and |VeNV μN * |2/(|VeN|2 + |VμN|2), where VℓN is the matrix element describing the mixing of N with the standard model neutrino of flavor ℓ = e, μ. For N masses between 20 and 1600 GeV, the upper limits on |VℓN|2 range between 2.3 × 10−5 and unity. These are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for production of Higgs boson pairs in the four b quark final state using large-area jets in proton-proton collisions at root s 13 TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search is presented for pair production of the standard model Higgs boson using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 35.9 fb−1. The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where one pair is highly Lorentz-boosted and is reconstructed as a single large-area jet, and the other pair is resolved and is reconstructed using two b-tagged jets. The results are obtained by combining this analysis with another from CMS looking for events with two large jets. Limits are set on the product of the cross sections and branching fractions for narrow bulk gravitons and radions in warped extradimensional models having a mass in the range 750-3000 GeV. The resulting observed and expected upper limits on the non-resonant Higgs boson pair production cross section correspond to 179 and 114 times the standard model value, respectively, at 95% confidence level. The existence of anomalous Higgs boson couplings is also investigated and limits are set on the non-resonant Higgs boson pair production cross sections for representative coupling values.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Search for heavy resonances decaying into two Higgs bosons or into a Higgs boson and a W or Z boson in proton-proton collisions at 13 TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search is presented for massive narrow resonances decaying either into two Higgs bosons, or into a Higgs boson and a W or Z boson. The decay channels considered are HH→bb⎯⎯⎯ + − and VH→qq⎯⎯⎯ + −, where H denotes the Higgs boson, and V denotes the W or Z boson. This analysis is based on a data sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV by the CMS Collaboration, corresponding to an integrated luminosity of 35.9 fb−1. For the TeV-scale mass resonances considered, substructure techniques provide ways to differentiate among the hadronization products from vector boson decays to quarks, Higgs boson decays to bottom quarks, and quark- or gluon-induced jets. Reconstruction techniques are used that have been specifically optimized to select events in which the tau lepton pair is highly boosted. The observed data are consistent with standard model expectations and upper limits are set at 95% confidence level on the product of cross section and branching fraction for resonance masses between 0.9 and 4.0 TeV. Exclusion limits are set in the context of bulk radion and graviton models:spin-0 radion resonances are excluded below a mass of 2.7 TeV at 95% confidence level. In the spin-1 heavy vector triplet framework, mass-degenerate W′ and Z′ resonances with dominant couplings to the standard model gauge bosons are excluded below a mass of 2.8 TeV at 95% confidence level. These are the first limits for massive resonances at the TeV scale with these decay channels at √=13 TeV.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurement of differential cross sections for inclusive isolated-photon and photon plus jet production in proton-proton collisions at root s=13TeV, European Physical Journal C: Particles and Fields, Vol: 79, ISSN: 1434-6044
Measurements of inclusive isolated-photon and photon+jet production in proton–proton collisions at √=13TeV are presented. The analysis uses data collected by the CMS experiment in 2015, corresponding to an integrated luminosity of 2.26fb−1. The cross section for inclusive isolated photon production is measured as a function of the photon transverse energy in a fiducial region. The cross section for photon+jet production is measured as a function of the photon transverse energy in the same fiducial region with identical photon requirements and with the highest transverse momentum jet. All measurements are in agreement with predictions from next-to-leading-order perturbative QCD.
Sirunyan AM, Tumasyan A, Adam W, et al., 2019, Measurement of inclusive and differential Higgs boson production cross sections in the diphoton decay channel in proton-proton collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
Measurements of the inclusive and differential production cross sections for the Higgs boson in the diphoton decay channel are performed using the data set of proton-proton collisions at √=13 TeV collected by the CMS experiment at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb−1. The cross sections are measured in a fiducial phase space defined by a set of requirements on the isolation and kinematic variables of the photons. Differential cross sections are measured as functions of the kinematic properties of the diphoton system and the event. A subset of the measurements is performed in regions of the fiducial phase space, where relative contributions of specific Higgs boson production mechanisms are enhanced. The total cross section in the chosen fiducial phase space is measured to be 84 ± 11 (stat) ± 7 (syst) fb = 84 ± 13 fb, to be compared with a theoretical prediction of 73 ± 4 fb. All measurements are found to be in agreement with the theoretical predictions for the standard model Higgs boson with a mass of 125.09 GeV within the experimental and theoretical uncertainties.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Observation of medium-induced modifications of jet fragmentation in Pb-Pb collisions at root s(NN)=5.02 TeV using isolated photon-tagged jets, Physical Review Letters, Vol: 121, ISSN: 0031-9007
Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with pjetT>30 GeV/c in events containing an isolated photon with pγT>60 GeV/c, using charged tracks with transverse momentum ptrkT>1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial pT and azimuthal angle of the parton whose shower produced the jet. For central Pb-Pb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central Pb-Pb events show an excess (depletion) of low (high) pT particles, with a transition around 3 GeV/c. This measurement shows for the first time the in-medium shower modifications of partons (quark dominated) with well-defined initial kinematics. It constitutes a new well-controlled reference for testing theoretical models of the parton passage through the quark-gluon plasma.
Sirunyan AM, Sirunyan AM, Tumasyan A, et al., 2018, Search for leptoquarks coupled to third-generation quarks in proton-proton collisions at root s=13 TeV, Physical Review Letters, Vol: 121, ISSN: 0031-9007
Three of the most significant measured deviations from standard model predictions, the enhanced decay rate for B→D(*)τν, hints of lepton universality violation in B→K(*)ℓℓ decays, and the anomalous magnetic moment of the muon, can be explained by the existence of leptoquarks (LQs) with large couplings to third-generation quarks and masses at the TeV scale. The existence of these states can be probed at the LHC in high energy proton-proton collisions. A novel search is presented for pair production of LQs coupled to a top quark and a muon using data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, recorded by the CMS experiment. No deviation from the standard model prediction has been observed and scalar LQs decaying exclusively into tμ are excluded up to masses of 1420 GeV. The results of this search are combined with those from previous searches for LQ decays into tτ and bν, which excluded scalar LQs below masses of 900 and 1080 GeV. Vector LQs are excluded up to masses of 1190 GeV for all possible combinations of branching fractions to tμ, tτ and bν. With this analysis, all relevant couplings of LQs with an electric charge of −1/3 to third-generation quarks are probed for the first time.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Angular analysis of the decay B+ -> K+mu(+)mu(-) in proton-proton collisions at root s=8 TeV, Physical Review D, Vol: 98, ISSN: 2470-0010
The angular distribution of the flavor-changing neutral current decay B+→K+μ+μ− is studied in proton-proton collisions at a center-of-mass energy of 8 TeV. The analysis is based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb−1. The forward-backward asymmetry AFB of the dimuon system and the contribution FH from the pseudoscalar, scalar, and tensor amplitudes to the decay width are measured as a function of the dimuon mass squared. The measurements are consistent with the standard model expectations.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV, Physical Review D, Vol: 98, ISSN: 2470-0010
A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb−1, from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling λ′′312 or λ′′323 and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the ˜t→qq′ scenario.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Event shape variables measured using multijet final states in proton-proton collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
The study of global event shape variables can provide sensitive tests of predictions for multijet production in proton-proton collisions. This paper presents a study of several event shape variables calculated using jet four momenta in proton-proton collisions at a centre-of-mass energy of 13 TeV and uses data recorded with the CMS detector at the LHC corresponding to an integrated luminosity of 2.2 fb−1. After correcting for detector effects, the resulting distributions are compared with several theoretical predictions. The agreement generally improves as the energy, represented by the average transverse momentum of the two leading jets, increases.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Evidence for the associated production of a single top quark and a photon in proton-proton collisions at sqrt[s]=13 TeV, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The first evidence of events consistent with the production of a single top quark in association with a photon is reported. The analysis is based on proton-proton collisions at sqrt[s]=13 TeV and recorded by the CMS experiment in 2016, corresponding to an integrated luminosity of 35.9 fb^{-1}. Events are selected by requiring the presence of a muon (μ), a photon (γ), an imbalance in transverse momentum from an undetected neutrino (ν), and at least two jets (j) of which exactly one is identified as associated with the hadronization of a b quark. A multivariate discriminant based on topological and kinematic event properties is employed to separate signal from background processes. An excess above the background-only hypothesis is observed, with a significance of 4.4 standard deviations. A fiducial cross section is measured for isolated photons with transverse momentum greater than 25 GeV in the central region of the detector. The measured product of the cross section and branching fraction is σ(pp→tγj)B(t→μνb)=115±17(stat)±30(syst) fb, which is consistent with the standard model prediction.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurements of Higgs boson properties in the diphoton decay channel in proton-proton collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
Measurements of Higgs boson properties in the H → γγ decay channel are reported. The analysis is based on data collected by the CMS experiment in proton-proton collisions at √=13 TeV during the 2016 LHC running period, corresponding to an integrated luminosity of 35.9 fb−1. Allowing the Higgs mass to float, the measurement yields a signal strength relative to the standard model prediction of 1.18 − 0.14 + 0.17 = 1.18 − 0.11 + 0.12 (stat) − 0.07 + 0.09 (syst) − 0.06 + 0.07 (theo), which is largely insensitive to the exact Higgs mass around 125 GeV. Signal strengths associated with the different Higgs boson production mechanisms, couplings to bosons and fermions, and effective couplings to photons and gluons are also measured.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos and b quarks at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for heavy resonances, decaying into the standard model vector bosons and the standard model Higgs boson, is presented. The final states considered contain a b quark-antiquark pair from the decay of the Higgs boson, along with electrons and muons and missing transverse momentum, due to undetected neutrinos, from the decay of the vector bosons. The mass spectra are used to search for a localized excess consistent with a resonant particle. The data sample corresponds to an integrated luminosity of 35.9 fb−1 collected in 2016 by the CMS experiment at the CERN LHC from proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with background expectations. Exclusion limits are set in the context of spin-0 two Higgs doublet models, some of which include the presence of dark matter. In the spin-1 heavy vector triplet framework, mass-degenerate W′ and Z′ resonances with dominant couplings to the standard model gauge bosons are excluded below a mass of 2.9 TeV at 95% confidence level.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for resonances in the mass spectrum of muon pairs produced in association with b quark jets in proton-proton collisions at root 8 and 13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for resonances in the mass range 12–70 GeV produced in association with a b quark jet and a second jet, and decaying to a muon pair, is reported. The analysis is based on data from proton-proton collisions at center-of-mass energies of 8 and 13 TeV, collected with the CMS detector at the LHC and corresponding to integrated luminosities of 19.7 and 35.9 fb−1, respectively. The search is carried out in two mutually exclusive event categories. Events in the first category are required to have a b quark jet in the central region (|η| ≤ 2.4) and at least one jet in the forward region (|η| > 2.4). Events in the second category are required to have two jets in the central region, at least one of which is identified as a b quark jet, no jets in the forward region, and low missing transverse momentum. An excess of events above the background near a dimuon mass of 28 GeV is observed in the 8 TeV data, corresponding to local significances of 4.2 and 2.9 standard deviations for the first and second event categories, respectively. A similar analysis conducted with the 13 TeV data results in a mild excess over the background in the first event category corresponding to a local significance of 2.0 standard deviations, while the second category results in a 1.4 standard deviation deficit. The fiducial cross section measurements and 95% confidence level upper limits on those for a resonance consistent with the 8 TeV excess are provided at both collision energies.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for supersymmetry in events with a tau lepton pair and missing transverse momentum in proton-proton collisions at root s=13TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for the electroweak production of supersymmetric particles in proton-proton collisions at a center-of-mass energy of 13 TeV is presented in final states with a τ lepton pair. Both hadronic and leptonic decay modes are considered for the τ leptons. Scenarios involving the direct pair production of τ sleptons, or their indirect production via the decays of charginos and neutralinos, are investigated. The data correspond to an integrated luminosity of 35.9 fb−1 collected with the CMS detector in 2016. The observed number of events is consistent with the standard model background expectation. The results are interpreted as upper limits on the cross section for τ slepton pair production in different scenarios. The strongest limits are observed in the scenario of a purely left-handed low mass τ slepton decaying to a nearly massless neutralino. Exclusion limits are also set in the context of simplified models of chargino-neutralino and chargino pair production with decays to τ leptons, and range up to 710 and 630 GeV, respectively.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Search for the decay of a Higgs boson in the ll gamma channel in proton-proton collisions at root s=13 TeV, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
A search for a Higgs boson decaying into a pair of electrons or muons and a photon is described. Higgs boson decays to a Z boson and a photon (H → Zγ → ℓℓγ, ℓ = e or μ), or to two photons, one of which has an internal conversion into a muon pair (H → γ*γ → μμγ) were considered. The analysis is performed using a data set recorded by the CMS experiment at the LHC from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. No significant excess above the background prediction has been found. Limits are set on the cross section for a standard model Higgs boson decaying to opposite-sign electron or muon pairs and a photon. The observed limits on cross section times the corresponding branching fractions vary between 1.4 and 4.0 (6.1 and 11.4) times the standard model cross section for H → γ*γ → μμγ (H → Zγ → ℓℓγ) in the 120–130 GeV mass range of the ℓℓγ system. The H → γ*γ → μμγ and H → Zγ →ℓℓγ analyses are combined for mH =125GeV, obtaining an observed (expected) 95% confidence level upper limit of 3.9 (2.0) times the standard model cross section.
Sirunyan AM, Tumasyan A, Adam W, et al., 2018, Measurement of differential cross sections for Z boson production in association with jets in proton- proton collisions at v s=13TeV, The European Physical Journal C, Vol: 78, ISSN: 1434-6044
The production of a Z boson, decaying to two charged leptons, in association with jets in proton-proton collisions at a centre-of-mass energy of 13TeV is measured. Data recorded with the CMS detector at the LHC are used that correspond to an integrated luminosity of 2.19fb-1. The cross section is measured as a function of the jet multiplicity and its dependence on the transverse momentum of the Z boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, which quantifies the hadronic activity, and the balance in transverse momentum between the reconstructed jet recoil and the Z boson. The measurements are compared with predictions from four different calculations. The first two merge matrix elements with different parton multiplicities in the final state and parton showering, one of which includes one-loop corrections. The third is a fixed-order calculation with next-to-next-to-leading order accuracy for the process with a Z boson and one parton in the final state. The fourth combines the fully differential next-to-next-to-leading order calculation of the process with no parton in the final state with next-to-next-to-leading logarithm resummation and parton showering.
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