İstanbul Gedik Üniversitesi Kurumsal Akademik Arşivi
DSpace@Gedik, İstanbul Gedik Üniversitesi tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Search for a scalar or pseudoscalar dilepton resonance produced in association with a massive vector boson or top quark-antiquark pair in multilepton events at √s=13 TeV
(American Physical Society, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
A search for beyond the standard model spin-0 bosons, phi, that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with a W or Z gauge boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision data set used in the analysis was collected at the LHC from 2016 to 2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138 fb(-1). The observations are consistent with the predictions from standard model processes. Upper limits are placed on the product of cross sections and branching fractions of such new particles over the mass range of 15 to 350 GeV with scalar, pseudoscalar, or Higgs-boson-like couplings, as well as on the product of coupling parameters and branching fractions. Several model-dependent exclusion limits are also presented. For a Higgs-boson-like phi model, limits are set on the mixing angle of the Higgs boson with the phi boson. For the associated production of a phi boson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and a fermiophilic axion-like model with pseudoscalar couplings.
Measurement of simplified template cross sections of the Higgs boson produced in association with W or Z bosons in the H → bb decay channel in proton-proton collisions at √s=13 TeV
(American Physical Society, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (Formula Presented, Formula Presented) and decaying to a pair of Formula Presented quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the Formula Presented and Formula Presented bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved Formula Presented-tagged jets, or from single large-radius jets containing the particles arising from two Formula Presented quarks. Proton-proton collision data at Formula Presented, collected by the CMS experiment in 2016-2018 and corresponding to a total integrated luminosity of Formula Presented, are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be Formula Presented. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.
Investigation of the electromagnetic shielding efficiency of FeB and Fe2B: ab-initio calculations
(Institute of Physics, 2024) Üşenti, Hakan; Duru, İzzet Paruğ
The electromagnetic (EM) pollution that we are exposed to in our daily lives has reached levels that threaten the health of living organisms and the stable operation of sensitive systems. The most effective way to protect against this pollution is to create isolated areas framed with shielding materials that can minimize the transmission of EM radiation. The development of shielding materials with high physical endurance against external factors to meet the needs of various sectors remains a popular research topic. This process, which started with metal plates, has continued with the development of doped polymers and composite materials. In recent years, materials with 2D structures have been developed. In this study, the shielding effectiveness (SE) of FeB and Fe2B nanostructures are revealed using ab initio calculations in Perdew-Burke-ErnzerhofSol scheme. SE has been widely figuring out via optical properties which are strongly related to mechanical and electronic properties herewith magnetic phases. The ferrimagnetic FeB and Fe2B nanostructures are considered. Besides, we focus on the thickness and photon energy dependent behavior along various projections. The findings demonstrate shielding performance at levels of >20 dB. Although both materials show similar shielding performance, it is observed that Fe2B is promising when compared to FeB. This study demonstrates that FeB and Fe2B, members of the MBene family, are promising materials not only because of their superior physical and chemical properties but also because of their shielding performance.
Correlation of proton conductivity and free volume in sulfonated polyether ether ketone electrolytes: a positron annihilation lifetime spectroscopy study
(Elsevier Ltd, 2025) Lahmuni, Muhammet; Yılmazoğlu, Mesut; Abacı, Ufuk; Çoban, Ozan; Yumak Yahşi, Ayse; Tav, Cumali; Yahşi, Uğur
Proton-conducting polymers play a pivotal role in clean energy technologies and various industrial applications, with a significant emphasis on enhancing energy efficiency and minimizing environmental impact. Sulfonated polyether ether ketone (SPEEK), which is renowned for its proton conductivity, has emerged as a key material in electrochemical processes, notably in proton exchange membrane (PEM) fuel cells. This study investigated the proton conductivity and dielectric behavior of SPEEK electrolytes at varying degree of sulfonation (DS) of 65% and 80%, correlating these properties with free volume profiles determined by positron annihilation lifetime spectroscopy (PALS). The SPEEK-65 and SPEEK-80 electrolytes were prepared via a controlled sulfonation process and characterized by FTIR, TGA, and SEM analyses. Proton conductivity and dielectric measurements were conducted at temperatures ranging from 300 to 370 K and frequencies ranging from 20 Hz to 1 MHz. The results revealed that SPEEK-80 exhibited a maximum proton conductivity of 3.4 × 10−2 S/m at 300 K and 1 MHz, which was significantly greater than the 4.38 × 10−3 S/m observed for SPEEK-65 under the same conditions. PALS analysis demonstrated a notable increase in free volume with increasing DS, with SPEEK-80 showing a higher o-Ps lifetime and intensity, indicating larger free volume sizes and fractions. These findings underscore the critical interplay between DS, free volume, and proton conductivity, offering insights into optimizing SPEEK-based electrolytes for advanced electrochemical applications.
Observation of the Υ(3S) meson and suppression of Υ states in Pb-Pb collisions at √sNN=5.02 TeV
(American Physical Society, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, S.; Damanakis, Konstantinos; Dragicevic, M.
The production of Upsilon(2S) and Upsilon(3S) mesons in lead-lead (Pb-Pb) and proton-proton (pp) collisions is studied in their dimuon decay channel using the CMS detector at the LHC. The Upsilon(3S) meson is observed for the first time in Pb-Pb collisions, with a significance above 5 standard deviations. The ratios of yields measured in Pb-Pb and pp collisions are reported for both the Upsilon(2S) and Upsilon(3S) mesons, as functions of transverse momentum and Pb-Pb collision centrality. These ratios, when appropriately scaled, are significantly less than unity, indicating a suppression of Upsilon yields in Pb-Pb collisions. This suppression increases from peripheral to central Pb-Pb collisions. Furthermore, the suppression is stronger for Upsilon(3S) mesons compared to Upsilon(2S) mesons, extending the pattern of sequential suppression of quarkonium states in nuclear collisions previously seen for the J/psi, psi(2S), Upsilon(1S), and Upsilon(2S) mesons.
