Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Laser. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks using a matrix element method

Abstract: A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5 inverse femtobarns collected by the CMS experiment at the LHC in pp collisions at a centre-of-mass energy of 8 TeV. In order to separate the signal from the larger ttbar+jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, mu, relative to the standard model prediction for a Higgs boson mass of 125 GeV. The observed (expected) exclusion limit at a 95% confidence level is mu < 4.2 (3.3), corresponding to a best fit value mu-hat = 1.2+1.6-1.5.

Study of the equilibrium processes in the gas phase during silicon carbide sublimation

Abstract: The thermodynamic analysis of the equilibrium processes in the gas phase during silicon carbide sublimation in the temperature interval 1500–2150 K is carried out. On the basis of the results of the thermodynamic analysis the composition of the equilibrium gas phase above silicon carbide and the “extents of the development” of reactions of silicon carbide dissociation and evaporation are determined. The thermodynamic analysis carried out is shown that the composition and the stoichiometry of the gas phase above silicon carbide depend very much on the temperature and it is necessary to take into account this dependence in the analysis of the growth processes of silicon carbide monocrystals and epitaxial layers.

Search for t(t)over-barH production in the all-jet final state in proton-proton collisions root s=13 TeV

Abstract: A search is presented for the associated production of a Higgs boson with a top quark pair in the all-jet final state. Events containing seven or more jets are selected from a sample of proton-proton collisions at $$ \sqrt{s}=13 $$ TeV collected with the CMS detector at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb−1. To separate the $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $$ signal from the irreducible $$ \mathrm{t}\overline{\mathrm{t}}+\mathrm{b}\overline{\mathrm{b}} $$ background, the analysis assigns leading order matrix element signal and background probability densities to each event. A likelihood-ratio statistic based on these probability densities is used to extract the signal. The results are provided in terms of an observed ttH signal strength relative to the standard model production cross section μ = σ/σSM, assuming a Higgs boson mass of 125 GeV. The best fit value is $$ \widehat{\mu}=0.9\pm 0.7\left(\mathrm{stat}\right)\pm 1.3\left(\mathrm{syst}\right)=0.9\pm 1.5\left(\mathrm{tot}\right) $$ , and the observed and expected upper limits are, respectively, μ < 3.8 and < 3.1 at 95% confidence levels.

Demonstration of cooling by the Muon Ionization Cooling Experiment

Abstract: Science and Technology Facilities Council (UK); Department of Energy and the National Science Foundation (USA); Istituto Nazionale di Fisica Nucleare (Italy); European Union’s Framework Programme 7 ; Japan Society for the Promotion of Science; National Research Foundation of Korea; Ministry of Education, Science and Technological Development of the Republic of Serbia; Institute of High Energy Physics; Chinese Academy of Sciences fund; National Science Foundation.