WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 239Citation - Scopus: 291Performance of the Cms Level-1 Trigger in Proton-Proton Collisions at √s = 13 Tev(Institute of Physics, 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Erö, J.; Bunichev, V.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. © 2020 CERN for the benefit of the CMS collaboration.Article Citation - WoS: 205Citation - Scopus: 159Search for Resonances and Quantum Black Holes Using Dijet Mass Spectra in Proton-Proton Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Hegeman, J.A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at s=8TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7fb-1. In a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 TeV. When interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 TeV; excited quarks below 3.5 TeV; scalar diquarks below 4.7 TeV; W′ bosons below 1.9 TeV or between 2.0 and 2.2 TeV; Z′ bosons below 1.7 TeV; and Randall-Sundrum gravitons below 1.6 TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 TeV, and color-octet scalars with mass below 2.5 TeV. Lower bounds between 5.0 and 6.3 TeV are set on the masses of quantum black holes. © 2015 CERN, for the CMS Collaboration.Article Citation - WoS: 518Citation - Scopus: 550Precise Determination of the Mass of the Higgs Boson and Tests of Compatibility of Its Couplings With the Standard Model Predictions Using Proton Collisions at 7 and 8 Tev(Springer Nature, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Janot, P.Properties of the Higgs boson with mass near 125 GeV are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include γγ, ZZ, WW, ττ, bb, and μμ pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1fb-1at 7TeV and up to 19.7fb-1at 8 TeV. From the high-resolution γγ and ZZ channels, the mass of the Higgs boson is determined to be (Formula presented) GeV. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is (Formula presented) at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found. © 2015, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 1Citation - Scopus: 6Search for Supersymmetry With Photons in Pp Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Calvo, E.Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7fb-1 of proton-proton collisions at s=8TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at the 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles. © 2015 CERN. © 2015 CERN, for the CMS Collaboration. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Article Citation - WoS: 154Citation - Scopus: 174Pileup Mitigation at Cms in 13 Tev Data(Institute of Physics, 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Erö, J.; Belyaev, A.With increasing instantaneous luminosity at the LHC come additional reconstruction challenges. At high luminosity, many collisions occur simultaneously within one proton-proton bunch crossing. The isolation of an interesting collision from the additional "pileup"collisions is needed for effective physics performance. In the CMS Collaboration, several techniques capable of mitigating the impact of these pileup collisions have been developed. Such methods include charged-hadron subtraction, pileup jet identification, isospin-based neutral particle "δβ"correction, and, most recently, pileup per particle identification. This paper surveys the performance of these techniques for jet and missing transverse momentum reconstruction, as well as muon isolation. The analysis makes use of data corresponding to 35.9 fb-1 collected with the CMS experiment in 2016 at a center-of-mass energy of 13 TeV. The performance of each algorithm is discussed for up to 70 simultaneous collisions per bunch crossing. Significant improvements are found in the identification of pileup jets, the jet energy, mass, and angular resolution, missing transverse momentum resolution, and muon isolation when using pileup per particle identification. © 2020 CERN for the benefit of the CMS collaboration..Article Citation - WoS: 65Citation - Scopus: 69Search for New Physics in Same-Sign Dilepton Events in Proton–proton Collisions at √s = 13 Tev(Springer Nature, 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Scodellaro, L.A search for new physics is performed using events with two isolated same-sign leptons, two or more jets, and missing transverse momentum. The results are based on a sample of proton–proton collisions at a center-of-mass energy of 13TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 2.3 fb1. Multiple search regions are defined by classifying events in terms of missing transverse momentum, the scalar sum of jet transverse momenta, the transverse mass associated with a W boson candidate, the number of jets, the number of b quark jets, and the transverse momenta of the leptons in the event. The analysis is sensitive to a wide variety of possible signals beyond the standard model. No excess above the standard model background expectation is observed. Constraints are set on various supersymmetric models, with gluinos and bottom squarks excluded for masses up to 1300 and 680GeV, respectively, at the 95 % confidence level. Upper limits on the cross sections for the production of two top quark-antiquark pairs (119fb) and two same-sign top quarks (1.7pb) are also obtained. Selection efficiencies and model independent limits are provided to allow further interpretations of the results. © 2016, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 68Citation - Scopus: 73Measurement of the W +w - Cross Section in Pp Collisions at √s= 8 Tevand Limits on Anomalous Gauge Couplings(Springer Nature, 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Albajar, C.A measurement of the W boson pair production cross section in proton-proton collisions at √s = 8 TeV is presented. The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 19.4fb-1. The W +W - candidates are selected from events with two charged leptons, electrons or muons, and large missing transverse energy. The measured W +W - cross section is 60.1 ± 0.9 (stat) ± 3.2 (exp) ± 3.1 (theo) ± 1.6 (lumi) pb = 60.1±4.8 pb, consistent with the standard model prediction. The W +W - cross sections are also measured in two different fiducial phase space regions. The normalized differential cross section is measured as a function of kinematic variables of the final-state charged leptons and compared with several perturbative QCD predictions. Limits on anomalous gauge couplings associated with dimension-six operators are also given in the framework of an effective field theory. The corresponding 95 % confidence level intervals are -5.7<cWWW/Λ2<5.9TeV-2, -11.4<cW/Λ2<5.4TeV-2, -29.2<cB/Λ2<23.9TeV-2, in the HISZ basis. © 2016, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 42Citation - Scopus: 86Measurement of the Double-Differential Inclusive Jet Cross Section in Proton–proton Collisions at √s = 13 Tev(Springer Nature, 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Matorras, F.A measurement of the double-differential inclusive jet cross section as a function of jet transverse momentum pT and absolute jet rapidity | y| is presented. The analysis is based on proton–proton collisions collected by the CMS experiment at the LHC at a centre-of-mass energy of 13TeV. The data samples correspond to integrated luminosities of 71 and 44pb-1 for | y| < 3 and 3.2 < | y| < 4.7 , respectively. Jets are reconstructed with the anti-kt clustering algorithm for two jet sizes, R, of 0.7 and 0.4, in a phase space region covering jet pT up to 2TeV and jet rapidity up to | y| = 4.7. Predictions of perturbative quantum chromodynamics at next-to-leading order precision, complemented with electroweak and nonperturbative corrections, are used to compute the absolute scale and the shape of the inclusive jet cross section. The cross section difference in R, when going to a smaller jet size of 0.4, is best described by Monte Carlo event generators with next-to-leading order predictions matched to parton showering, hadronisation, and multiparton interactions. In the phase space accessible with the new data, this measurement provides a first indication that jet physics is as well understood at s=13TeV as at smaller centre-of-mass energies. © 2016, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 38Citation - Scopus: 38Search for Heavy Resonances Decaying To Two Higgs Bosons in Final States Containing Four B Quarks(Springer Nature, 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Garcia-Ferrero, J.A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at s=8TeV. The data correspond to an integrated luminosity of 19.7fb-1. The search considers H H resonances with masses between 1 and 3TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t t ¯ events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 % confidence level for the product of the production cross section and branching fraction σ(gg→X)B(X→HH→bb¯bb¯) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0TeV, significantly extending previous searches. For a warped extra dimension theory with a mass scale ΛR= 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55TeV. © 2016, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 18Citation - Scopus: 18Search for Direct Pair Production of Supersymmetric Top Quarks Decaying To All-Hadronic Final States in Pp Collisions at √s = 8 Tev(Springer Nature, 2016) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Castiñeiras De Saa, J.R.Results are reported from a search for the pair production of top squarks, the supersymmetric partners of top quarks, in final states with jets and missing transverse momentum. The data sample used in this search was collected by the CMS detector and corresponds to an integrated luminosity of 18.9fb-1 of proton-proton collisions at a centre-of-mass energy of 8TeV produced by the LHC. The search features novel background suppression and prediction methods, including a dedicated top quark pair reconstruction algorithm. The data are found to be in agreement with the predicted backgrounds. Exclusion limits are set in simplified supersymmetry models with the top squark decaying to jets and an undetected neutralino, either through a top quark or through a bottom quark and chargino. Models with the top squark decaying via a top quark are excluded for top squark masses up to 755GeV in the case of neutralino masses below 200GeV. For decays via a chargino, top squark masses up to 620GeV are excluded, depending on the masses of the chargino and neutralino. © 2016, CERN for the benefit of the CMS collaboration.