Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Brandstetter, J.Department: search.filters.department.İzmir Institute of Technology

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  • Article
    Citation - WoS: 15
    Citation - Scopus: 19
    Study of J/Ψ Meson Production Inside Jets in pp Collisions at S=8 TeV
    (Elsevier B.V., 2020) Karapınar, Güler; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Hensel, C.; 01. Izmir Institute of Technology
    A study of the production of prompt J/ψ mesons contained in jets in proton-proton collisions at s=8TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb−1 collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/ψ meson and the jet is used to test whether the J/ψ meson is part of the jet. The analysis shows that most prompt J/ψ mesons having energy above 15 GeV and rapidity |y|<1 are contained in jets with pseudorapidity |η<inf>jet</inf>|<1. The differential distributions of the probability to have a J/ψ meson contained in a jet as a function of jet energy for a fixed J/ψ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/ψ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/ψ production using nonrelativistic quantum chromodynamics. © 2020 Elsevier B.V.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Measurements With Silicon Photomultipliers of Dose-Rate Effects in the Radiation Damage of Plastic Scintillator Tiles in the Cms Hadron Endcap Calorimeter
    (Institute of Physics, 2020) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Dimova, T.; 01. Izmir Institute of Technology
    Measurements are presented of the reduction of signal output due to radiation damage for two types of plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb-1. The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: A laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions. Results from several irradiation campaigns using 60Co sources are also discussed. The damage is presented as a function of dose rate. Within the range of these measurements, for a fixed dose the damage increases with decreasing dose rate. © 2020 CERN for the benefit of the CMS collaboration..
  • Article
    Citation - WoS: 6
    Citation - Scopus: 10
    Study 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.; 01. Izmir Institute of Technology
    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: 8
    Citation - Scopus: 17
    Measurement of the Associated Production of a Z Boson With Charm or Bottom Quark Jets in Proton-Proton Collisions at S =13 Tev
    (American Physical Society, 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Tyurin, N.; 01. Izmir Institute of Technology
    Ratios of cross sections, σ(Z+c jets)/σ(Z+jets), σ(Z+b jets)/σ(Z+jets), and σ(Z+c jets)/σ(Z+b jets) in the associated production of a Z boson with at least one charm or bottom quark jet are measured in proton-proton collisions at s=13 TeV. The data sample, collected by the CMS experiment at the CERN LHC, corresponds to an integrated luminosity of 35.9 fb-1, with a fiducial volume of pT>30 GeV and |η|<2.4 for the jets, where pT and η represent transverse momentum and pseudorapidity, respectively. The Z boson candidates come from leptonic decays into electrons or muons with pT>25 GeV and |η|<2.4, and the dilepton mass satisfies 71<mZ<111 GeV. The measured values are σ(Z+c jets)/σ(Z+jets)=0.102±0.002±0.009, σ(Z+b jets)/σ(Z+jets)=0.0633±0.0004±0.0015, and σ(Z+c jets)/σ(Z+b jets)=1.62±0.03±0.15. Results on the inclusive and differential cross section ratios as functions of jet and Z boson transverse momentum are compared with predictions from leading and next-to-leading order perturbative quantum chromodynamics calculations. These are the first measurements of the cross section ratios at 13 TeV. © 2020 American Physical Society. All rights reserved.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Mechanical Stability of the Cms Strip Tracker Measured With a Laser Alignment System
    (Institute of Physics, 2017) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Soares, M.S.; 01. Izmir Institute of Technology
    The CMS tracker consists of 206 m2 of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from -25 to +25°C. The mechanical stability of tracker components during physics operation was monitored with a few μm resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011-2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30μm. In addition, temperature variations were found to cause displacements of tracker structures of about 2μm°C, which largely revert to their initial positions when the temperature is restored to its original value. © CERN 2017 for the benefit of the CMS collaboration..
  • Article
    Citation - WoS: 33
    Citation - Scopus: 45
    Measurement 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.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Barney, D.; 01. Izmir Institute of Technology
    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: 33
    Citation - Scopus: 38
    Search for Dark Matter Produced in Association With Heavy-Flavor Quark Pairs in Proton-Proton Collisions at √s=13tev
    (Springer Nature, 2017) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Dorney, B.; 01. Izmir Institute of Technology
    A search is presented for an excess of events with heavy-flavor quark pairs (tt¯ and bb¯) and a large imbalance in transverse momentum in data from proton–proton collisions at a center-of-mass energy of 13TeV. The data correspond to an integrated luminosity of 2.2fb-1 collected with the CMS detector at the CERN LHC. No deviations are observed with respect to standard model predictions. The results are used in the first interpretation of dark matter production in tt¯ and bb¯ final states in a simplified model. This analysis is also the first to perform a statistical combination of searches for dark matter produced with different heavy-flavor final states. The combination provides exclusions that are stronger than those achieved with individual heavy-flavor final states. © 2017, CERN for the benefit of the CMS collaboration.
  • Article
    Citation - WoS: 314
    Citation - Scopus: 714
    Particle-Flow Reconstruction and Global Event Description With the Cms Detector
    (Institute of Physics, 2017) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Abbaneo, D.; 01. Izmir Institute of Technology
    The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider. For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic τ decay reconstruction, missing transverse momentum determination, and electron and muon identification. This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods. The data collected by CMS at a centre-of-mass energy of 8\TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions. © 2017 CERN.
  • Article
    Citation - WoS: 59
    Citation - Scopus: 73
    Cross Section Measurement of T-Channel Single Top Quark Production in Pp Collisions at S=13tev
    (Elsevier B.V., 2017) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Rodrigo, T.; 01. Izmir Institute of Technology
    The cross section for the production of single top quarks in the t channel is measured in proton–proton collisions at 13TeV with the CMS detector at the LHC. The analyzed data correspond to an integrated luminosity of 2.2fb−1. The event selection requires one muon and two jets where one of the jets is identified as originating from a bottom quark. Several kinematic variables are then combined into a multivariate discriminator to distinguish signal from background events. A fit to the distribution of the discriminating variable yields a total cross section of 238±13(stat)±29(syst) pb and a ratio of top quark and top antiquark production of Rt-ch.=1.81±0.18(stat)±0.15(syst). From the total cross section the absolute value of the CKM matrix element Vtb is calculated to be 1.05±0.07(exp)±0.02(theo). All results are in agreement with the standard model predictions. © 2017 The Author(s)
  • Article
    Citation - WoS: 13
    Citation - Scopus: 15
    Study of Dijet Events With a Large Rapidity Gap Between the Two Leading Jets in Pp Collisions at √s=7tev
    (Springer Nature, 2018) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Bloch, P.; 01. Izmir Institute of Technology
    Events with no charged particles produced between the two leading jets are studied in proton-proton collisions at s=7TeV. The jets were required to have transverse momentum pTjet>40GeV and pseudorapidity 1.5 < | ηjet| < 4.7 , and to have values of ηjet with opposite signs. The data used for this study were collected with the CMS detector during low-luminosity running at the LHC, and correspond to an integrated luminosity of 8pb-1. Events with no charged particles with pT> 0.2 GeV in the interval - 1 < η< 1 between the jets are observed in excess of calculations that assume no color-singlet exchange. The fraction of events with such a rapidity gap, amounting to 0.5–1% of the selected dijet sample, is measured as a function of the pT of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky–Fadin–Kuraev–Lipatov evolution equations, including different models of the non-perturbative gap survival probability. © 2018, CERN for the benefit of the CMS collaboration.