Szerző szerinti böngészés "Khachatryan, V."
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Tétel Szabadon hozzáférhető A search for pair production of new light bosons decaying into muons(2016) Khachatryan, V.; Makovec, Alajos; Raics, Péter; Trócsányi, Zoltán; Ujvári, BalázsTétel Szabadon hozzáférhető Angular analysis and branching fraction measurement of the decay B0→K*0μ+μ-Chatrchyan, S.; Khachatryan, V.; Sirunyan, A.M.; J. Karancsi; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemThe angular distributions and the differential branching fraction of the decay B0→K*(892)0μ+μ- are studied using a data sample corresponding to an integrated luminosity of 5.2fb-1 collected with the CMS detector at the LHC in pp collisions at s=7TeV. From more than 400 signal decays, the forward-backward asymmetry of the muons, the K*(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions.Tétel Szabadon hozzáférhető Azimuthal decorrelation of jets widely separated in rapidity in pp collisions at √s = 7 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Raics Péter (1944-) (fizikus); Makovec Alajos (1987-) (fizikus); Fizikai Intézet -- 749; TTK; Debreceni EgyetemThe decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at the LHC at s=7 TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Δϕ, between the Mueller-Navelet jets, the average cosines of (π − Δϕ), 2(π − Δϕ), and 3(π − Δϕ), and ratios of these cosines. The jets are required to have transverse momenta, pT, in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Δy, between the Mueller-Navelet jets, reaching Δy up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes.Tétel Szabadon hozzáférhető Combined search for anomalous pseudoscalar HVV couplings in VH(H→bb‾) production and H → VV decayKhachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Fizikai Intézet -- 749; TTK; Debreceni EgyetemA search for anomalous pseudoscalar couplings of the Higgs boson H to electroweak vector bosons V (=W or Z) in a sample of proton–proton collision events corresponding to an integrated luminosity of 18.9 fb−1 at a center-of-mass energy of 8 TeV is presented. Events consistent with the topology of associated VH production, where the Higgs boson decays to a pair of bottom quarks and the vector boson decays leptonically, are analyzed. The consistency of data with a potential pseudoscalar contribution to the HVV interaction, expressed by the effective pseudoscalar cross section fractions fa, is assessed by means of profile likelihood scans. Results are given for the VH channels alone and for a combined analysis of the VH and previously published H→VV channels. Under certain assumptions, fa ZZ>0.0034 is excluded at 95% confidence level in the combination. Scenarios in which these assumptions are relaxed are also considered.Tétel Szabadon hozzáférhető Constraints on parton distribution functions and extraction of the strong coupling constant from the inclusive jet cross section in pp collisions at √s = 7 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; A. Makovec; P. Raics; Z. L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemThe inclusive jet cross section for proton–proton collisions at a centre-of-mass energy of 7,TeV was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of (Formula Presented.). The measurement covers a phase space up to 2, TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass (Formula Presented.), which is in agreement with the world average.Tétel Szabadon hozzáférhető Constraints on the pMSSM, AMSB model and on other models from the search for long-lived charged particles in proton–proton collisions at √s = 8 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; A. Makovec; P. Raics; Z. L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemStringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton–proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.Tétel Szabadon hozzáférhető Constraints on the spin-parity and anomalous HVV couplings of the Higgs boson in proton collisions at 7 and 8 TeV(2015) Khachatryan, V.; Karancsi, János; Makovec, Alajos; Raics, Péter; Trócsányi, Zoltán; Ujvári, BalázsTétel Szabadon hozzáférhető Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at s=7 TeVKhachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; J. Karancsi; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemMeasurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb−1. The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.Tétel Szabadon hozzáférhető Distributions of topological observables in inclusive three- and four-jet events in pp collisions at √S=7 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; A. Makovec; P. Raics; Z. L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemThis paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7$$\,\text {TeV}$$TeV with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1$$\,\text {fb}^{-1}$$fb-1. The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, MadGraph interfaced with pythia6 displays the overall best agreement withdata.Tétel Szabadon hozzáférhető Erratum: search for new physics in events with same-sign dileptons and b jets in pp collisions at √s=8 TeVChatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; J. Karancsi; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemTétel Szabadon hozzáférhető Erratum: Search for new physics in events with same-sign dileptons and jets in pp collisions at √s = 8 TeVChatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; J. Karancsi, P. Raics, Z.L. Trocsanyi, B. Ujvari; Karancsi János (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemTétel Szabadon hozzáférhető Evidence for Collective Multiparticle Correlations in p-Pb Collisions(2015) Khachatryan, V.; Karancsi, János; Makovec, Alajos; Raics, Péter; Trócsányi, Zoltán; Ujvári, BalázsTétel Szabadon hozzáférhető Evidence for exclusive γγ → W+ W− production and constraints on anomalous quartic gauge couplings in pp collisions at √s = 7 and 8 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Raics Péter (1944-) (fizikus); Makovec Alajos (1987-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Fizikai Intézet -- 749; TTK; Debreceni EgyetemA search for exclusive or quasi-exclusive γγ → W+W− production, via pp → p(*)W+W−p(*) → p(*)μ±e∓p(*) at √s = 8 TeV, is reported using data corresponding to an integrated luminosity of 19.7 fb−1. Events are selected by requiring the presence of an electron-muon pair with large transverse momentum pT(μ±e∓) > 30 GeV, and no associated charged particles detected from the same vertex. The 8 TeV results are combined with the previous 7 TeV results (obtained for 5.05 fb−1 of data). In the signal region, 13 (2) events are observed over an expected background of 3.9 ± 0.6 (0.84 ± 0.15) events for 8 (7) TeV, resulting in a combined excess of 3.4σ over the background-only hypothesis. The observed yields and kinematic distributions are compatible with the standard model prediction for exclusive and quasi-exclusive γγ → W+W− production. Upper limits on the anomalous quartic gauge coupling operators a0,C W (dimension-6) and fM0,1,2,3 (dimension-8), the most stringent to date, are derived from the measured dilepton transverse momentum spectrum.Tétel Szabadon hozzáférhető Forward–backward asymmetry of Drell–Yan lepton pairs in pp collisions at √s = 8 TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Fizikai Intézet -- 749; TTK; Debreceni EgyetemA measurement of the forward–backward asymmetry AFB of oppositely charged lepton pairs (μμ and ee) produced via Z / γ∗ boson exchange in pp collisions at √s = 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.7 fb-1 collected with the CMS detector at the LHC. The measurement of AFB is performed for dilepton masses between 40 GeV and 2TeV and for dilepton rapidity up to 5. The AFB measurements as a function of dilepton mass and rapidity are compared with the standard model predictions.Tétel Szabadon hozzáférhető Inclusive and differential measurements of the tt¯ charge asymmetry in pp collisions at √s=8 TeVKhachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z.L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Fizikai Intézet -- 749; TTK; Debreceni EgyetemThe tt¯ charge asymmetry is measured in proton–proton collisions at a centre-of-mass energy of 8 TeV. The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 fb−1. Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010±0.0068 (stat)±0.0037 (syst). In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the tt¯ system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of −0.0035±0.0072 (stat)±0.0031 (syst). All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model.Tétel Szabadon hozzáférhető Inclusive search for supersymmetry using razor variables in pp collisions at root{s} = 13 TeV(2017) Khachatryan, V.; Karancsi, János; Bartók, Márton; Raics, Péter; Trócsányi, Zoltán; Ujvári, BalázsTétel Szabadon hozzáférhető Limits on the Higgs boson lifetime and width from its decay to four charged leptonsKhachatryan, V.; Sirunyan, A. M.; Tumasyan; J. Karancsi; M. Bartók; A. Makovec; P. Raics; Z. L. Trocsanyi; B. Ujvari; Karancsi János (1987-) (fizikus); Bartók Márton (2024-) (xxx); Makovec Alajos (1987-) (fizikus); Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemConstraints on the lifetime and width of the Higgs boson are obtained from H→ZZ→4ℓ events using data recorded by the CMS experiment during the LHC run 1 with an integrated luminosity of 5.1 and 19.7fb-1 at a center-of-mass energy of 7 and 8 TeV, respectively. The measurement of the Higgs boson lifetime is derived from its flight distance in the CMS detector with an upper bound of τH<1.9×10-13s at the 95% confidence level (C.L.), corresponding to a lower bound on the width of ΓH>3.5×10-9MeV. The measurement of the width is obtained from an off-shell production technique, generalized to include anomalous couplings of the Higgs boson to two electroweak bosons. From this measurement, a joint constraint is set on the Higgs boson width and a parameter fΛQ that expresses an anomalous coupling contribution as an on-shell cross-section fraction. The limit on the Higgs boson width is ΓH<46MeV with fΛQ unconstrained and ΓH<26MeV for fΛQ=0 at the 95% C.L. The constraint fΛQ<3.8×10-3 at the 95% C.L. is obtained for the expected standard model Higgs boson width.Tétel Szabadon hozzáférhető [Magdi] Dijet azimuthal decorrelations in pp collisions at √s=7TeVKhachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; P. Raics; Z. L. Trocsanyi; B. Ujvari; Smith, W. H.; Swanson, J.; Weinberg, M.; Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemMeasurements of dijet azimuthal decorrelations in pp collisions at √s=7TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9pb-1. The results are compared to predictions from perturbative QCD calculations and various Monte Carlo event generators. The dijet azimuthal distributions are found to be sensitive to initial-state gluon radiation.Tétel Szabadon hozzáférhető [Magdi] First measurement of hadronic event shapes in pp collisions at s=7 TeVKhachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; P. Raics; Z.L. Trocsanyi; B. Ujvari; Smith, W.H.; Swanson, J.; Weinberg, M.; Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemHadronic event shapes have been measured in proton–proton collisions at s=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 pb−1. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.Tétel Szabadon hozzáférhető [Magdi] Search for supersymmetry in pp collisions at 7 TeV in events with jets and missing transverse energyKhachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; P. Raics; Z.L. Trocsanyi; B. Ujvari; Smith, W.H.; Swanson, J.; Weinberg, M.; Raics Péter (1944-) (fizikus); Trócsányi Zoltán (1961-) (fizikus); Ujvári Balázs (1977-) (Fizikus / PhD); Debreceni EgyetemA search for supersymmetry with R-parity conservation in proton–proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 pb −1 collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely tt¯, W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders.