Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 39Citation - Scopus: 48Analysis of the Cp Structure of the Yukawa Coupling Between the Higgs Boson and Tau Leptons in Proton-Proton Collisions at Root S=13 Tev(Springer, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Del Valle, A. EscalanteThe first measurement of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons is presented. The measurement is based on data collected in proton-proton collisions at root s = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1). The analysis uses the angular correlation between the decay planes of tau leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd tau Yukawa couplings is found to be -1 +/- 19 degrees, compared to an expected value of 0 +/- 21 degrees at the 68.3% confidence level. The data disfavour the pure CP-odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.Correction Correction To: “curved Space and Particle Physics Effects on the Formation of Bose–einstein Condensation Around a Reissner–nordstrøm Black Hole”(Springer, 2022) Erdem, Recai; Demirkaya, Betül; Gültekin, KemalAfter this correction Fig. 1 in [1] is replaced by Fig. 1 above which is essentially the same as the one in [1]. Figure 2 in [1] now becomes irrelevant. Figure 3 in [1] is replaced by Fig. 2 above which is essentially the same as the one in [1].Article Citation - WoS: 2Citation - Scopus: 2Curved Space and Particle Physics Effects on the Formation of Bose-Einstein Condensation Around a Reissner-Nordstrom Black Hole(Springer, 2021) Erdem, Recai; Demirkaya, Betül; Gültekin, KemalWe consider two scalar fields interacting through a chi*chi phi*phi term in the presence of a Reissner-Nordstrom black hole. Initially, only chi particles are present. We find that the produced phi particles are localized in a region around the black hole and have a tendency toward condensation provided that phi particles are much heavier than the chi particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges.Article Citation - WoS: 2Citation - Scopus: 2Particle Physics Processes in Cosmology Through an Effective Minkowski Space Formulation and the Limitations of the Method(Springer, 2021) Erdem, Recai; Gültekin, KemalWe introduce a method where particle physics processes in cosmology may be calculated by the usual perturbative flat space quantum field theory through an effective Minkowski space description at small time intervals provided that the running of the effective particle masses are sufficiently slow. We discuss the necessary conditions for the applicability of this method and illustrate the method through a simple example. This method has the advantage of avoiding the effects of gravitational particle creation in the calculation of rates and cross sections i.e. giving directly the rates and the cross sections due to the scatterings or the decay processes.Conference Object Native and Light Induced Defect States in Wide Band Gap Hydrogenated Amorphous Silicon-Carbon (a-Si1 : H) Alloy Thin Films(Springer, 1997) Güneş, MehmetIn this study, wide band gap a-Si1-x C-x:H alloy thin films prepared with and without hydrogen diluation of (SiH4, CH4) were characterized using optical absorption, dark conductivity, steady-state photoconductivity, sub-bandgap absorption obtained with both photothermal deflection spectroscopy (PDS) and dual beam photoconductivity (DBP), and electron spin resonance (ESR) techniques. Experimental results of steady-state photoconductivity and sub-bandgap absorption for different generation rates were analyzed using a detailed numerical model based on Simmons-Taylor statistics. The densities, energy location and nature of the native and light induced defect states in diluted and undiluted a-Si1-xCx:H alloy thin films were derived from the best fits to the experimental data. The extracted parameters for defect states were compared with those of a-Si:H films both in the annealed and light degraded states.Article Citation - WoS: 9Citation - Scopus: 7Epitaxial Characteristics of Mbe-Grown Znte Thin Films on Gaas (211)b Substrates(Springer, 2019) Özçeri, Elif; Tarhan, EnverHighly crystalline ZnTe thin films were grown on GaAs (211)B substrates by molecular beam epitaxy (MBE) for potential applications such as MCT detectors and optoelectronic devices. We investigated the effects of Te to Zn (VI/II) flux ratio on the quality of ZnTe films in terms of crystal orientation, elemental composition, surface roughness, and dislocation density. Atomic concentrations of Zn, Te, and oxygen complexes due to oxygen contamination on the film surfaces were analyzed by X-ray photoelectron spectroscopy. X-ray double crystal rocking curve full width half maximum (FWHM) of ZnTe (422) peak was observed as 233 arcseconds for a 1.66 mu m thick film, which indicates high crystallinity. Wet chemical etching was applied to the films to quantify the crystal quality by calculating etch pit densities (EPD) from scanning electron microscope images. A very low EPD value of 1.7 x 10(7) cm(-2) was measured. Additionally, the root mean square roughness values, obtained from atomic force microscopy topography images were in the range of 10-25 nm. These values were supported by FWHM values of red green blue color intensity histograms obtained from Nomarski Microscope images. The results of our analyses indicate that the VI/II flux ratios of 4 and 4.5 produce the best quality ZnTe films on GaAs (211)B substrates.Article Citation - WoS: 1Citation - Scopus: 2Extended Dynamical Symmetries of Landau Levels in Higher Dimensions(Springer, 2020) Kürkçüoğlu, Seçkin; Ünal, Gizem; Yurduşen, IsmetContinuum models for time-reversal (TR) invariant topological insulators (Tis) in d >= 3 dimensions are provided by harmonic oscillators coupled to certain SO(d) gauge fields. These models are equivalent to the presence of spin-orbit (SO) interaction in the oscillator Hamiltonians at a critical coupling strength (equivalent to the harmonic oscillator frequency) and leads to flat Landau Level (LL) spectra and therefore to infinite degeneracy of either the positive or the negative helicity states depending on the sign of the SO coupling. Generalizing the results of [1] to d >= 4, we construct vector operators commuting with these Hamiltonians and show that SO(d, 2) emerges as the non-compact extended dynamical symmetry. Focusing on the model in four dimensions, we demonstrate that the infinite degeneracy of the flat spectra can be fully explained in terms of the discrete unitary representations of SO(4,2), i.e. the doubletons. The degeneracy in the opposite helicity branch is finite, but can still be explained exploiting the complex conjugate doubleton representations. Subsequently, the analysis is generalized to d-dimensions, distinguishing the cases of odd and even d. We also determine the spectrum generating algebra in these models and briefly comment on the algebraic organization of the LL states w.r.t. an underlying "deformed" AdS geometry as well as on the organization of the surface states under open boundary conditions in view of our results.Article Citation - WoS: 13Citation - Scopus: 13Thermodynamics of Regular Black Holes With Cosmic Strings(Springer, 2018) Bayraktar, Ceren H.In this article, the thermodynamics of regular black holes with a cosmic string passing through them is studied. We will observe that the string has no effect on the temperature as well as on the relation between entropy S and horizon area A.Article Citation - WoS: 6Citation - Scopus: 10Effect of Annealing on the Density of Defects in Epitaxial Cdte (211)/Gaas(Springer, 2018) Bakali, Emine; Selamet, Yusuf; Tarhan, EnverCdTe thin films were grown on GaAs (211) wafers by molecular beam epitaxy as the buffer layer for HgCdTe infrared detector applications. We studied the effect of annealing on the density of dislocation of these CdTe thin films under varying annealing parameters such as annealing temperature, annealing duration, and number of cycles. Annealings were carried out using a homemade annealing reactor possessing a special heater element made of a Si wafer for rapid heating. The density of dislocations, which were made observable with a scanning electron microscope after etching with an Everson solution, were calculated by counting the number of dislocations per unit surface area, hence the term etch pit density (EPD). We were able to decrease EPD values by one order of magnitude after annealing. For example, the best EPD value after a 20-min annealing at 400°C was ∼ 2 × 107 cm−2 for a 1.63-μm CdTe thin film which was about 9.5 × 107 cm−2 before annealing. We also employed Raman scattering measurements to see the changes in the structural quality of the samples. From the Raman measurements, we were able to see improvements in the quality of our samples from the annealing by studying the ratio of 2LO/LO phonon mode Raman intensities. We also observed a clear decrease in the intensity of Te precipitations-related modes, indicating a decrease in the size and number of these precipitations.