Physics / Fizik
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Article Single Layer Res2h2: Stability, Raman Activity and Electronic Properties(Eskişehir Teknik Üniversitesi, 2018) Ünsal, Elif; Şahin, HasanIn this study, the structural, vibrational and electronic properties of the hydrogenated single layer of ReS2 are investigated byperforming the first principle calculations based on density functional theory. We found that the characteristic properties ofthe monolayer ReS2 can be manipulated upon the hydrogen functionalization. As the monolayer ReS2, the ReS2H2 hasdistorted 1T phase; however, the bonding in Re slab significantly varies with the hydrogenation. Our results demonstrate thatthe full-surface hydrogenation leads to an expansion in lattice and the Re4 tetramer-chains in the monolayer ReS2 areseparated into two dimers in the hydrogenated monolayer. It is calculated that the dynamically stable monolayer of ReS2H2has 26 Raman-active vibrational modes. Constant volume specific heat calculations are also performed and the resultsindicate that at high temperature, the monolayer ReS2 approaches to limit of 3R before the monolayer ReS2H2. By performingthe electronic band structure calculations, it is shown that when the ReS2 surface is fully hydrogenated, there occurs a directto indirect band gap transition and the semiconducting hydrogen-induced monolayer has a band gap of 0.74 eV.Article Citation - WoS: 28Search for a Heavy Bottom-Like Quark in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA search for pair-produced bottom-like quarks in pp collisions at root s = 7 TeV is conducted with the CMS experiment at the LHC. The decay b' -> tW is considered in this search. The b'(b) over bar' tW-(t) over barW(+) process can be identified by the distinctive signature of trileptons and same-sign dileptons. With a data sample corresponding to an integrated luminosity of 34 pb(-1), no excess above the standard model background predictions is observed and a b' quark with a mass between 255 and 361 GeV/c(2) is excluded at the 95% confidence level. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 21Measurement of the Ratio of the 3-Jet To 2-Jet Cross Sections in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum. HT, in the range 0.2 < H-T < 2.5 TeV is presented. The data have been collected at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb(-1). Comparisons are made between the data and the predictions of different QCD-based Monte Carlo models for multijet production. All models considered in this study are consistent with the data for H-T > 0.5 TeV. This measurement extends to an H-T range that has not been explored before. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 33Search for Physics Beyond the Standard Model Using Multilepton Signatures in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA search for physics beyond the standard model in events with at least three leptons and any number of jets is presented. The data sample corresponds to 35 pb(-1) of integrated luminosity in pp collisions at root s = 7 TeV collected by the CMS experiment at the LHC. A number of exclusive multileptonic channels are investigated and standard model backgrounds are suppressed by requiring sufficient missing transverse energy, invariant mass inconsistent with that of the Z boson, or high jet activity. Control samples in data are used to ascertain the robustness of background evaluation techniques and to minimise the reliance on simulation. The observations are consistent with background expectations. These results constrain previously unexplored regions of supersymmetric parameter space. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 63Citation - Scopus: 73Angular Analysis and Branching Fraction Measurement of the Decay B-0 -> K*(0)mu(+)mu(-)(Elsevier, 2013) Demir, Durmuş Ali; Karapınar, GülerThe angular distributions and the differential branching fraction of the decay B-0 -> K*(892)(0)mu(+)mu(-) are studied using a data sample corresponding to an integrated luminosity of 5.2 fb(-1) collected with the CMS detector at the LHC in pp collisions at root s = 7 TeV. 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. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 15Ag and Au Atoms Intercalated in Bilayer Heterostructures of Transition Metal Dichalcogenides and Graphene(American Institute of Physics, 2014) İyikanat, Fadıl; Şahin, Hasan; Senger, Ramazan Tuğrul; Peeters, François M.The diffusive motion of metal nanoparticles Au and Ag on monolayer and between bilayer heterostructures of transition metal dichalcogenides and graphene are investigated in the framework of density functional theory. We found that the minimum energy barriers for diffusion and the possibility of cluster formation depend strongly on both the type of nanoparticle and the type of monolayers and bilayers. Moreover, the tendency to form clusters of Ag and Au can be tuned by creating various bilayers. Tunability of the diffusion characteristics of adatoms in van der Waals heterostructures holds promise for controllable growth of nanostructures. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.Article Citation - WoS: 16Citation - Scopus: 16Riemann-Eddington Theory: Incorporating Matter, Degravitating the Cosmological Constant(American Physical Society, 2014) Demir, Durmuş AliHere we show that Eddington's pure affine gravity, when extended with Riemann curvature, leads to gravitational field equations that incorporate matter. This Riemanned Eddington gravity outfits a setup in which matter gravitates normally with Newton's constant but vacuum gravitates differently with an independent gravitational constant. This novel setup enables degravitation of the vacuum to observed level not by any fine-tuning but by a large hierarchy between its gravitational constant and its energy density. Remarkably, degravitation of the cosmological constant is local, causal and natural yet only empirical because the requisite degravitation condition is not predicted by the theory.Article Citation - WoS: 36Citation - Scopus: 37Microwave Control of Rydberg Atom Interactions(Iop Publishing Ltd, 2014) Sevinçli, Sevilay; Pohl, T.We investigate the interaction between Rydberg atoms, whose electronic states are dressed by multiple microwave fields. Numerical calculations are used for an exact description of the microwave induced interactions, and employed to benchmark a perturbative treatment that yields simple insights into the involved mechanisms. Based on this theory, we demonstrate that microwave dressing provides a powerful approach to control dipolar as well as van der Waals interactions and even permits us to turn them off entirely. In addition, the proposed scheme also opens up possibilities for engineering dominant three-body interactions.Article Citation - WoS: 100Citation - Scopus: 81Search for Physics Beyond the Standard Model in Final States With a Lepton and Missing Transverse Energy in Proton-Proton Collisions at Root S = 8 Tev(American Physical Society, 2015) Demir, Durmuş Ali; Karapınar, GülerA search for new physics in proton-proton collisions having final states with an electron or muon and missing transverse energy is presented. The analysis uses data collected in 2012 with the CMS detector, at an LHC center-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of 19.7 fb(-1). No significant deviation of the transverse mass distribution of the charged lepton-neutrino system from the standard model prediction is found. Mass exclusion limits of up to 3.28 TeVat 95% confidence level for a W0-boson with the same couplings as that of the standard model W-boson are determined. Results are also derived in the framework of split universal extra dimensions, and exclusion limits on Kaluza-Klein Wd(KK)((2)) states are found. The final state with large missing transverse energy also enables a search for dark matter production with a recoiling W-boson, with limits set on the mass and the production cross section of potential candidates. Finally, limits are established for a model including interference between a left-handed W'-boson and the standard model W-boson and for a compositeness model.Article Citation - WoS: 32Citation - Scopus: 34The Cms Barrel Calorimeter Response To Particle Beams From 2 To 350 Gev/C(Springer Verlag, 2009) CMS HCAL/ECAL Collaborations; Sönmez, NasufThe response of the CMS barrel calorimeter (electromagnetic plus hadronic) to hadrons, electrons and muons over a wide momentum range from 2 to 350 GeV/c has been measured. To our knowledge, this is the widest range of momenta in which any calorimeter system has been studied. These tests, carried out at the H2 beam-line at CERN, provide a wealth of information, especially at low energies. The analysis of the differences in calorimeter response to charged pions, kaons, protons and antiprotons and a detailed discussion of the underlying phenomena are presented. We also show techniques that apply corrections to the signals from the considerably different electromagnetic (EB) and hadronic (HB) barrel calorimeters in reconstructing the energies of hadrons. Above 5 GeV/c, these corrections improve the energy resolution of the combined system where the stochastic term equals 84.7 ± 1.6% and the constant term is 7.4 ± 0.8%. The corrected mean response remains constant within 1.3% rms. © Springer-Verlag / Società Italiana di Fisica 2009.