Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 51Citation - Scopus: 60Identification of Hadronic Tau Lepton Decays Using a Deep Neural Network(Institute of Physics, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Andreev, V.; 01. Izmir Institute of TechnologyA new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons (τ h) that originate from genuine tau leptons in the CMS detector against τ h candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τ h candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine τ h to pass the discriminator against jets increases by 10-30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τ h reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τ h reconstruction method are validated with LHC proton-proton collision data at s = 13 TeV. © 2022 CERN.Article Citation - WoS: 11Citation - Scopus: 11Measurements 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 TechnologyMeasurements 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: 114Citation - Scopus: 138Identification of Heavy, Energetic, Hadronically Decaying Particles Using Machine-Learning Techniques(Institute of Physics, 2020) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic, M.; Okhotnikov, V.; 01. Izmir Institute of TechnologyMachine-learning (ML) techniques are explored to identify and classify hadronic decays of highly Lorentz-boosted W/Z/Higgs bosons and top quarks. Techniques without ML have also been evaluated and are included for comparison. The identification performances of a variety of algorithms are characterized in simulated events and directly compared with data. The algorithms are validated using proton-proton collision data at s = 13TeV, corresponding to an integrated luminosity of 35.9 fb-1. Systematic uncertainties are assessed by comparing the results obtained using simulation and collision data. The new techniques studied in this paper provide significant performance improvements over non-ML techniques, reducing the background rate by up to an order of magnitude at the same signal efficiency. © 2020 CERN for the benefit of the CMS collaboration..Article Citation - WoS: 678Citation - Scopus: 550The Cms Trigger System(Institute of Physics, 2017) Khachatryan, V.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; de Trocóniz, J.F.; 01. Izmir Institute of TechnologyThis paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described. © CERN 2017 for the benefit of the CMS collaboration..Article Citation - WoS: 1Citation - Scopus: 1Mechanical 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 TechnologyThe 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: 314Citation - Scopus: 714Particle-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 TechnologyThe 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: 202Citation - Scopus: 497Identification of Heavy-Flavour Jets With the Cms Detector in Pp Collisions at 13 Tev(Institute of Physics, 2018) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Sanchez Cruz, S.; 01. Izmir Institute of TechnologyMany measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse momenta in the range expected in simulated events, these new developments result in an efficiency of 68% for the correct identification of a b jet for a probability of 1% of misidentifying a light-flavour jet. The improvement in relative efficiency at this misidentification probability is about 15%, compared to previous CMS algorithms. In addition, for the first time algorithms have been developed to identify jets containing two b hadrons in Lorentz-boosted event topologies, as well as to tag c jets. The large data sample recorded in 2016 at a centre-of-mass energy of 13 TeV has also allowed the development of new methods to measure the efficiency and misidentification probability of heavy-flavour jet identification algorithms. The b jet identification efficiency is measured with a precision of a few per cent at moderate jet transverse momenta (between 30 and 300 GeV) and about 5% at the highest jet transverse momenta (between 500 and 1000 GeV). © 2018 CERN for the benefit of the CMS collaboration.Article Citation - WoS: 11Citation - Scopus: 13Precision Measurement of the Structure of the Cms Inner Tracking System Using Nuclear Interactions(Institute of Physics, 2018) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Karjavin, V.; 01. Izmir Institute of TechnologyThe structure of the CMS inner tracking system has been studied using nuclear interactions of hadrons striking its material. Data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2015 at the LHC are used to reconstruct millions of secondary vertices from these nuclear interactions. Precise positions of the beam pipe and the inner tracking system elements, such as the pixel detector support tube, and barrel pixel detector inner shield and support rails, are determined using these vertices. These measurements are important for detector simulations, detector upgrades, and to identify any changes in the positions of inactive elements. © 2018 CERN for the benefit of the CMS collaboration.Article Citation - WoS: 34Citation - Scopus: 49Performance of the Reconstruction and Identification of High-Momentum Muons in Proton-Proton Collisions at S = 13 Tev(Institute of Physics, 2020) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic, M.; Volkov, A.; 01. Izmir Institute of TechnologyThe CMS detector at the LHC has recorded events from proton-proton collisions, with muon momenta reaching up to 1.8 TeV in the collected dimuon samples. These high-momentum muons allow direct access to new regimes in physics beyond the standard model. Because the physics and reconstruction of these muons are different from those of their lower-momentum counterparts, this paper presents for the first time dedicated studies of efficiencies, momentum assignment, resolution, scale, and showering of very high momentum muons produced at the LHC. These studies are performed using the 2016 and 2017 data sets of proton-proton collisions at s = 13 TeV with integrated luminosities of 36.3 and 42.1 fb-1, respectively. © 2020 CERN for the benefit of the CMS collaboration..Review Citation - WoS: 4Citation - Scopus: 6Calibration of the Cms Hadron Calorimeters Using Proton-Proton Collision Data at S = 13 Tev(Institute of Physics, 2020) Sirunyan, A.M.; Karapınar, Güler; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Klyukhin, V.; 01. Izmir Institute of TechnologyMethods are presented for calibrating the hadron calorimeter system of the CMS detector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities |η| < 3 and are positioned inside the solenoidal magnet. An outer calorimeter, outside the magnet coil, covers |η| < 1.26, and a steel and quartz-fiber Cherenkov forward calorimeter extends the coverage to |η| < 5.19. The initial calibration of the calorimeters was based on results from test beams, augmented with the use of radioactive sources and lasers. The calibration was improved substantially using proton-proton collision data collected at s = 7, 8, and 13 TeV, as well as cosmic ray muon data collected during the periods when the LHC beams were not present. The present calibration is performed using the 13 TeV data collected during 2016 corresponding to an integrated luminosity of 35.9 fb-1. The intercalibration of channels exploits the approximate uniformity of energy collection over the azimuthal angle. The absolute energy scale of the central and endcap calorimeters is set using isolated charged hadrons. The energy scale for the electromagnetic portion of the forward calorimeters is set using Z→ ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy. © 2020 CERN for the benefit of the CMS collaboration..