Mühendislik ve Doğa Bilimleri Fakültesi Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/1624

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Now showing 1 - 14 of 14

Citation - WoS: 37
Citation - Scopus: 59
Inclusive Nonresonant Multilepton Probes of New Phenomena at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Güler, Yalçın; The CMS Collaboration
An inclusive search for nonresonant signatures of beyond the standard model (SM) phenomena in events with three or more charged leptons, including hadronically decaying tau leptons, is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 138 fb(-1) of proton-proton collisions at root s = 13 TeV, collected by the CMS experiment at the LHC in 2016-2018. Events are categorized based on the lepton and b-tagged jet multiplicities and various kinematic variables. Three scenarios of physics beyond the SM are probed, and signal-specific boosted decision trees are used for enhancing sensitivity. No significant deviations from the background expectations are observed. Lower limits are set at 95% confidence level on the mass of type-III seesaw heavy fermions in the range 845-1065 GeV for various decay branching fraction combinations to SM leptons. Doublet and singlet vectorlike tau lepton extensions of the SM are excluded for masses below 1045 GeV and in the mass range 125-150 GeV, respectively. Scalar leptoquarks decaying exclusively to a top quark and a lepton are excluded below 1.12-1.42 TeV, depending on the lepton flavor. For the type-III seesaw as well as the vectorlike doublet model, these constraints are the most stringent to date. For the vectorlike singlet model, these are the first constraints from the LHC experiments. Detailed results are also presented to facilitate alternative theoretical interpretations.
Citation - WoS: 61
Citation - Scopus: 68
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
(Amer Physical Soc, 2021) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Gürpınar Güler, Emine; Güler, Yalçın; The CMS Collaboration
Measurements of differential and double-differential cross sections of top-quark pair (t (t) over bar) production arc 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 p(T), where the top-quark decay products can be identified as separated jets and isolated leptons, and with high p(T), where the decay products are collimated and overlap. The measurements arc based on proton-proton collision data at is - = 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) over bar production cross section is measured to be sigma(t (t) over bar) = 791 +/- 25 pb, which constitutes the most precise measurement in the lepton + jets channel to date.
Citation - WoS: 5
Citation - Scopus: 26
Measurement of the Inclusive and Differential Higgs Boson Production Cross Sections in the Decay Mode To a Pair of Tau Leptons in Pp Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
Measurements of the inclusive and differential fiducial cross sections of the Higgs boson are presented, using the tau lepton decay channel. The differential cross sections are measured as functions of the Higgs boson transverse momentum, jet multiplicity, and transverse momentum of the leading jet in the event, if any. The analysis is performed using proton-proton collision data collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb-1. These are the first differential measurements of the Higgs boson cross section in the final state of two tau leptons. In final states with a large jet multiplicity or with a Lorentz-boosted Higgs boson, these measurements constitute a significant improvement over measurements performed in other final states.
Citation - WoS: 10
Citation - Scopus: 16
Measurement of the Production Cross Section for Z Plus B Jets in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Güler, Yalçın; The CMS Collaboration
The measurement of the cross section for the production of a Z boson, decaying to dielectrons or dimuons, in association with at least one bottom quark jet is performed with proton-proton collision data at p1/4 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb-1, collected by the CMS experiment at the LHC during 2016???2018. The integrated cross sections for Z?? > 1 b jet and Z?? > 2 b jets are reported for the electron, muon, and combined channels. The fiducial cross sections in the combined channel are 6.52 ??? 0.04??stat?? ??? 0.40??syst?? ??? 0.14??theo?? pb for Z?? > 1 b jet and 0.65 ??? 0.03??stat?? ??? 0.07??syst?? ??? 0.02??theo?? pb for Z?? > 2 b jets. The differential cross section distributions are measured as functions of various kinematic observables that are useful for precision tests of perturbative quantum chromodynamics predictions. The ratios of integrated and differential cross sections for Z?? > 2b jets and Z?? > 1 b jet processes are also determined. The value of the integrated cross section ratio measured in the combined channel is 0.100 ??? 0.005??stat?? ??? 0.007??syst?? ??? 0.003??theo??. All measurements are compared with predictions from various event generators.
Citation - WoS: 19
Measurement of W-+/-gamma Differential Cross Sections in Proton-Proton Collisions at Root S=13 Tev and Effective Field Theory Constraints
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
Differential cross section measurements of W(+/-)y production in proton-proton collisions at root s = 13 TeV are presented. The data set used in this study was collected with the CMS detector at the CERN LHC in 2016-2018 with an integrated luminosity of 138 fb(-1). Candidate events containing an electron or muon, a photon, and missing transverse momentum are selected. The measurements are compared with standard model predictions computed at next-to-leading and next-to-next-to-leading orders in perturbative quantum chromodynamics. Constraints on the presence of TeV-scale new physics affecting the WW gamma vertex are determined within an effective field theory framework, focusing on the O-3w operator. A simultaneous measurement of the photon transverse momentum and the azimuthal angle of the charged lepton in a special reference frame is performed. This two-dimensional approach provides up to a factor of ten more sensitivity to the interference between the standard model and the O-3w contribution than using the transverse momentum alone.
Citation - WoS: 15
Citation - Scopus: 21
Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at Root S=5.02 Tev Using Leptonic Decays
(Amer Physical Soc, 2021) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Gürpınar Güler, Emine; Güler, Yalçın; The CMS Collaboration
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 sigma(WW) = 37:0(-5.2)(+5.5) (stat)(-2.6)(+2.7) (syst) pb, sigma(WZ) = 6.4(-2.1)(+2.5) (stat)(-0.3)(+0.5)(syst) pb, and sigma(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.
Citation - WoS: 22
Citation - Scopus: 24
Observation of the B-C(+) Meson in Pb-Pb and Pp Collisions at Root S(nn)=5.02 Tev and Measurement of Its Nuclear Modification Factor
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
The B-c(+) meson is observed for the first time in heavy ion collisions. Data from the CMS detector are used to study the production of the B-c(+) meson in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a center of-mass energy per nucleon pair of root s(NN) = 5.02 TeV, via the B-c(+) -> (J/psi -> mu(+)mu(-))mu(+)nu(mu) decay. The B-c(+) nuclear modification factor, derived from the Pb-Pb-to-pp ratio of production cross sections, is measured in two bins of the trimuon transverse momentum and of the Pb-Pb collision centrality. The B-c(+) meson is shown to be less suppressed than quarkonia and most of the open heavy-flavor mesons, suggesting that effects of the hot and dense nuclear matter created in heavy ion collisions contribute to its production. This measurement sets forth a promising new probe of the interplay of suppression and enhancement mechanisms in the production of heavy-flavor mesons in the quark-gluon plasma.
Citation - WoS: 20
Citation - Scopus: 25
Precision Measurement of the W Boson Decay Branching Fractions in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
The leptonic and inclusive hadronic decay branching fractions of the W boson are measured using proton-proton collision data collected at p s = 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb???1. Events characterized by the production of one or two W bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of b quarks. A binned maximum likelihood estimate of the W boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the W boson decaying into electron, muon, and tau lepton final states are (10.83 ?? 0.10)%, (10.94 ?? 0.08)%, and (10.77 ?? 0.21)%, respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be (10.89 ?? 0.08)% and (67.32 ?? 0.23)%, respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo???Kobayashi???Maskawa (CKM) matrix Pij IVijI2 = 1.984 ?? 0.021, the CKM element IVcsI = 0.967 ?? 0.011, and the strong coupling constant at the W boson mass scale, ??S(m2W) = 0.095 ?? 0.033.
Citation - WoS: 9
Citation - Scopus: 13
Probing Charm Quark Dynamics Via Multiparticle Correlations in Pb-Pb Collisions at Root S(nn)=5.02 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
Multiparticle azimuthal correlations of prompt D-0 mesons arc measured in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02 TeV. For the first time, a four-particle cumulant method is used to extract the second Fourier coefficient of the azimuthal distribution (v(2)) of D-0 mesons as a function of event centrality and the D-0 transverse momentum. The ratios of the four-particle v(2) values to previously measured two-particle cumulant results provide direct experimental access to event-by-event fluctuations of charm quark azimuthal anisotropies. These ratios are also found to be comparable to those of inclusive charged particles in the event. However, hints of deviations are seen in the most central and peripheral collisions. To investigate the origin of flow fluctuations in the charm sector, these measurements are compared to a model implementing fluctuations of charm quark energy loss via collisional or radiative processes in the quark-gluon plasma. These models cannot quantitatively describe the data over the full transverse momentum and centrality ranges, although the calculations with collisional energy loss provide a better description of the data.
Citation - WoS: 19
Citation - Scopus: 29
Search for Flavor-Changing Neutral Current Interactions of the Top Quark and Higgs Boson in Final States With Two Photons in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1.) No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t -> Hu) and 0.073% (0.051%) for B(t -> Hc). These are the strictest upper limits yet determined.
Citation - WoS: 81
Citation - Scopus: 90
Search for Invisible Decays of the Higgs Boson Produced Via Vector Boson Fusion in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Güler, Yalçın; The CMS Collaboration
A search for invisible decays of the Higgs boson produced via vector boson fusion (VBF) has been performed with 101 fb(-1) of proton-proton collisions delivered by the LHC at root s = 13 TeV and collected by the CMS detector in 2017 and 2018. The sensitivity to the VBF production mechanism is enhanced by constructing two analysis categories, one based on missing transverse momentum and a second based on the properties of jets. In addition to control regions with Z and W boson candidate events, a highly populated control region, based on the production of a photon in association with jets, is used to constrain the dominant irreducible background from the invisible decay of a Z boson produced in association with jets. The results of this search arc combined with all previous measurements in the VBF topology, based on data collected in 2012 (at root s = 8 TeV), 2015, and 2016, corresponding to integrated luminosities of 19.7, 2.3, and 36.3 fb(-1), respectively. The observed (expected) upper limit on the invisible branching fraction of the Higgs boson is found to be 0.18 (0.10) at the 95% confidence level, assuming the standard model production cross section. The results are also interpreted in the context of Higgs-portal models.
Citation - WoS: 30
Citation - Scopus: 42
Search for Long-Lived Particles Decaying in the Cms End Cap Muon Detectors in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2021) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb(-1) of proton-proton collisions at root s = 13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and tau(+)tau(-) are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.
Citation - WoS: 5
Citation - Scopus: 7
Search for Resonances Decaying To Three W Bosons in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Güler, Yalçın; The CMS Collaboration
A search for resonances decaying into a W boson and a radion, where the radion decays into two W bosons, is presented. The data analyzed correspond to an integrated luminosity of 138 fb???1 recorded in ffiffiproton-proton collisions with the CMS detector at p s 1/4 13 TeV. One isolated charged lepton is required, together with missing transverse momentum and one or two massive large-radius jets, containing the decay products of either two or one W bosons, respectively. No excess over the background estimation is observed. The results are combined with those from a complementary channel with an all-hadronic final state, described in an accompanying paper. Limits are set on parameters of an extended warped extradimensional model. These searches are the first of their kind at the LHC.
Citation - WoS: 1
Citation - Scopus: 4
Search for Resonances Decaying To Three W Bosons in the Hadronic Final State in Proton-Proton Collisions at Root S=13 Tev
(Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Güler, Yalçın; The CMS Collaboration
A search for Kaluza-Klein excited vector boson resonances, WKK, decaying in cascade to three W bosons via a scalar radion R, WKK ??? WR ??? WWW, in a final state containing two or three massive jets is presented. The search is performed with ffis ffi p = 13 TeV proton-proton collision data collected by the CMS Two final states are simultaneously probed, one where the two W bosons produced by the R decay are reconstructed as separate, large-radius, massive jets, and one where they are merged into a single largeradius jet. The observed data are in agreement with the standard model expectations. Limits are set on the product of the WKK resonance cross section and branching fraction to three W bosons in an extended warped extra-dimensional model and are the first of their kind at the LHC.

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