PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7645
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Article Citation - WoS: 86Citation - Scopus: 8Measurement of Single-Diffractive Dijet Production in Proton–proton Collisions at √s=8te With the Cms and Totem Experiments(Springer Nature, 2020) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Josa, M.I.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 pp→pX and pp→Xp, 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=8Te 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 σjjpX, in the kinematic region ξ< 0.1 , 0.03<|t|<1Ge2, with at least two jets with transverse momentum pT>40Ge, and pseudorapidity | η| < 4.4 , is 21.7±0.9(stat)-3.3+3.0(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 ≤ log 10x≤ - 1.6 , is R=(σjjpX/Δξ)/σjj=0.025±0.001(stat)±0.003(syst), where σjjpX 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. © 2020, CERN for the benefit of the CMS and TOTEM collaborations.Article Citation - WoS: 6Citation - Scopus: 10Study of Central Exclusive [inlineequation Not Available: See Fulltext.] Production in Proton-Proton Collisions at √s=5.02 and 13tev(Springer Nature, 2020) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Kachanov, V.Central exclusive and semiexclusive production of [InlineEquation not available: see fulltext.] pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central [InlineEquation not available: see fulltext.] production are measured as functions of invariant mass, transverse momentum, and rapidity of the [InlineEquation not available: see fulltext.] system in the fiducial region defined as transverse momentum [InlineEquation not available: see fulltext.] and pseudorapidity [InlineEquation not available: see fulltext.]. The production cross sections for the four resonant channels [InlineMediaObject not available: see fulltext.], [InlineEquation not available: see fulltext.], [InlineMediaObject not available: see fulltext.], and [InlineMediaObject not available: see fulltext.]are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13TeV. © 2020, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 14Citation - Scopus: 21Evidence for Top Quark Production in Nucleus-Nucleus Collisions(American Physical Society, 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic, M.; Polikarpov, S.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 (σtt) 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, σtt=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. © 2020 CERN.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: 39Citation - Scopus: 43Measurement of the Wz Production Cross Section in Pp Isions at √s=7 and 8 Tev and Search for Anomalous Triple Gauge Couplings at √s=8tev(Springer Nature, 2017) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Fernandez, M.The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton–proton collision data samples corresponding to integrated luminosities of 4.9fb-1 collected at s=7TeV, and 19.6fb-1 at s=8TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71<mZ<111GeV are σ(pp→WZ;s=7TeV)=20.14±1.32(stat)±0.38(theo)±1.06(exp)±0.44(lumi)pb and σ(pp→WZ;s=8TeV)=24.09±0.87(stat)±0.80(theo)±1.40(exp)±0.63(lumi)pb. Differential cross sections with respect to the Z boson pT, the leading jet pT, and the number of jets are obtained using the s=8TeV data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 29Citation - Scopus: 33Measurement of the Jet Mass in Highly Boosted T T ¯ Events From Pp Collisions at √s=8tev(Springer Nature, 2017) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Baillon, P.The first measurement of the jet mass mjet of top quark jets produced in t t ¯ events from pp collisions at s=8TeV is reported for the jet with the largest transverse momentum pT in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7fb-1. The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay t → b W with W → ℓν where ℓ is an electron or muon, are used to select t t ¯ events with large Lorentz boosts. The products of the fully hadronic decay t → b W with W → q q ¯ ′ are reconstructed using a single Cambridge–Aachen jet with distance parameter R= 1.2 , and pT> 400 GeV. The t t ¯ cross section as a function of mjet is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the mjet distribution is sensitive to the top quark mass mt, and the data are used to extract a value of mt to assess this sensitivity. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 33Citation - Scopus: 45Measurement of the Triple-Differential Dijet Cross Section in Proton-Proton Collisions at √s=8tev and Constraints on Parton Distribution Functions(Springer Nature, 2017) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Barney, D.A measurement is presented of the triple-differential dijet cross section at a centre-of-mass energy of 8TeV using 19.7fb-1 of data collected with the CMS detector in proton-proton collisions at the LHC. The cross section is measured as a function of the average transverse momentum, half the rapidity separation, and the boost of the two leading jets in the event. The cross section is corrected for detector effects and compared to calculations in perturbative quantum chromodynamics at next-to-leading order accuracy, complemented with electroweak and nonperturbative corrections. New constraints on parton distribution functions are obtained and the inferred value of the strong coupling constant is αS(MZ)=0.1199±0.0015(exp)-0.0020+0.0031(theo), where MZ is the mass of the Z boson. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 67Citation - Scopus: 74Measurement of Double-Differential Cross Sections for Top Quark Pair Production in Pp Collisions at √s=8tev and Impact on Parton Distribution Functions(Springer Nature, 2017) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Ball, A.H.Normalized double-differential cross sections for top quark pair (t t ¯) production are measured in pp collisions at a centre-of-mass energy of 8TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7fb-1. The measurement is performed in the dilepton e ±μ∓ final state. The t t ¯ cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and t t ¯ system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured t t ¯ cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 104Citation - Scopus: 119Search for New Phenomena With the Mt 2 Variable in the All-Hadronic Final State Produced in Proton–proton Collisions at √s=13tev(Springer Nature, 2017) Sirunyan, A.M.; Tumasyan, A.; Johnson, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Scodellaro, L.A search for new phenomena is performed using events with jets and significant transverse momentum imbalance, as inferred through the MT 2 variable. The results are based on a sample of proton–proton collisions collected in 2016 at a center-of-mass energy of 13TeV with the CMS detector and corresponding to an integrated luminosity of 35.9fb-1. No excess event yield is observed above the predicted standard model background, and the results are interpreted as exclusion limits at 95% confidence level on the masses of predicted particles in a variety of simplified models of R-parity conserving supersymmetry. Depending on the details of the model, 95% confidence level lower limits on the gluino (light-flavor squark) masses are placed up to 2025 (1550)GeV. Mass limits as high as 1070 (1175)GeV are set on the masses of top (bottom) squarks. Information is provided to enable re-interpretation of these results, including model-independent limits on the number of non-standard model events for a set of simplified, inclusive search regions. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 56Citation - Scopus: 70Search for Standard Model Production of Four Top Quarks With Same-Sign and Multilepton Final States in Proton–proton Collisions at √s=13tev(Springer Nature, 2018) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Romero, L.A search for standard model production of four top quarks (t t ¯ t t ¯) is reported using events containing at least three leptons (e , μ) or a same-sign lepton pair. The events are produced in proton–proton collisions at a center-of-mass energy of 13TeV at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9fb-1. Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the t t ¯ t t ¯ cross section is measured to be 16.9-11.4+13.8fb, in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level. © 2018, CERN for the benefit of the CMS collaboration.
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