Yazar "Dragicevic M." seçeneğine göre listele
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Öğe Azimuthal Correlations within Exclusive Dijets with Large Momentum Transfer in Photon-Lead Collisions(American Physical Society, 2023) Tumasyan A.; Adam W.; Bergauer T.; Dragicevic M.; Del Valle A.E.; Frühwirth R.; CMS CollaborationThe structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at s NN = 5.02 TeV , corresponding to an integrated luminosity of 0.38 nb - 1 , collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects. © 2023 CERN, for the CMS Collaboration.Öğe Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC(IOP Publishing Ltd., 2021) Sirunyan, A. M.; Tumasyan A.; Adam, W.; Bergauer, T.; Dragicevic M.; Escalante Del Valle A.; Sağır, Sinan; CMS CollaborationThe performance is presented of the reconstruction and identification algorithms for electrons and photons with the CMS experiment at the LHC. The reported results are based on proton-proton collision data collected at a center-of-mass energy of 13 TeV and recorded in 2016-2018, corresponding to an integrated luminosity of 136 fb-1. Results obtained from lead-lead collision data collected at √sNN=5.02 TeV are also presented. Innovative techniques are used to reconstruct the electron and photon signals in the detector and to optimize the energy resolution. Events with electrons and photons in the final state are used to measure the energy resolution and energy scale uncertainty in the recorded events. The measured energy resolution for electrons produced in Z boson decays in proton-proton collision data ranges from 2 to 5%, depending on electron pseudorapidity and energy loss through bremsstrahlung in the detector material. The energy scale in the same range of energies is measured with an uncertainty smaller than 0.1 (0.3)% in the barrel (endcap) region in proton-proton collisions and better than 1 (3)% in the barrel (endcap) region in heavy ion collisions. The timing resolution for electrons from Z boson decays with the full 2016-2018 proton-proton collision data set is measured to be 200 ps.Öğe Evaluation of HPK n+-p planar pixel sensors for the CMS Phase-2 upgrade(Elsevier B.V., 2023) Adam W.; Bergauer T.; Damanakis K.; Dragicevic M.; Frühwirth R.; Steininger H.; Beaumont W.To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 1034cm?2s?1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to ?eq= 3.5 × 1016cm?2. This paper focuses on planar pixel sensor design and qualification up to a fluence of ?eq = 1.4 × 1016cm?2. For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150mm (6”) wafers with an active thickness of 150µm with pixel sizes of 100×25 µm2 and 50×50 µm2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50×50 µm2 pixels is measured as 4.0µm for non-irradiated samples, and 6.3µm after irradiation to ?eq = 7.2 × 1015cm?2. © 2023 Elsevier B.V.Öğe Measurement of the Z boson differential production cross section using its invisible decay mode (Z → νν¯) in proton-proton collisions at √s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2021) Sirunyan, A. M.; Tumasyan A.; Adam, W.; Bergauer, T.; Dragicevic M.; Escalante Del Valle A.; Sağır, Sinan; CMS CollaborationMeasurements of the total and differential fiducial cross sections for the Z boson decaying into two neutrinos are presented at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected by the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb−1. In these measurements, events are selected containing an imbalance in transverse momentum and one or more energetic jets. The fiducial differential cross section is measured as a function of the Z boson transverse momentum. The results are combined with a previous measurement of charged-lepton decays of the Z boson. The measured total fiducial cross section for events with Z boson transverse momentum greater than 200 GeV is 3000−170+180 fb.Öğe Measurements of the differential cross sections of the production of Z + jets and γ + jets and of Z boson emission collinear with a jet in pp collisions at √s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2021) Sirunyan, A. M.; Tumasyan A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic M.; Sağır, Sinan; CMS CollaborationMeasurements of the differential cross sections of Z + jets and γ + jets production, and their ratio, are presented as a function of the boson transverse momentum. Measurements are also presented of the angular distribution between the Z boson and the closest jet. The analysis is based on pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb−1 recorded by the CMS experiment at the LHC. The results, corrected for detector effects, are compared with various theoretical predictions. In general, the predictions at higher orders in perturbation theory show better agreement with the measurements. This work provides the first measurement of the ratio of the differential cross sections of Z + jets and γ + jets production at 13 TeV, as well as the first direct measurement of Z bosons emitted collinearly with a jet. [Figure not available: see fulltext.]
