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 & Standard Model. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

J/ψ and ψ (2S) production in pp collisions at √s = 7 TeV

Abstract: A measurement of the J/psi and psi(2S) production cross sections in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of 37 inverse picobarns. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B to psi(2S) X decay is extracted from the ratio of the non-prompt cross sections to be: BR(B to psi(2S) X) = (3.08 +/- 0.12(stat.+syst.) +/- 0.13(theor.) +/- 0.42(BR[PDG])) 10^-3

Photocatalytic properties of TiO2 modified with gold nanoparticles in the degradation of oxalic acid in aqueous solution

Abstract: The commercially available TiO 2 -catalyst (Degussa P25) was supported by spray pyrolysis deposition method on the outer surface of the quartz tubes, incorporated in photocatalytic reactor. The crystal structure and the morphology of the films were studied. The immobilized TiO 2 is modified with nanosized gold particles by the photoreduction method to obtain different noble metal loading (0.05–0.4 wt.%). The characterization of the synthesized catalysts was carried out by the BET method, X-ray photoelectron spectroscopy (XPS), SEM, TEM and the adsorption of the model pollutant was determined. The degradation of oxalic acid has been studied in aqueous solution photocatalyzed by band-gap-irradiated TiO 2 , modified with nanosized gold particles. The presence of low amounts of gold on the TiO 2 surface leads to an increase of its photocatalytic activity. The maximum value of the photocatalytic activity was registered with the ≈0.16 wt.% Au on TiO 2 sample. At this concentration the activity of the Au-modified TiO 2 is approximately double that of the semiconducting support. The adsorption properties of the catalysts, as well as the noble metal content on the surface of the support, influence the efficiency of the photocatalytic process. The reaction rate of photocatalytic degradation of the oxalic acid follows a zero kinetic order according to the Langmuir–Hinshelwood model.

Protection of densely populated excited triplet state ensembles against deactivation by molecular oxygen

Abstract: This critical review discusses different approaches towards protection of photoactive materials based on triplet excited state ensembles against deactivation by molecular oxygen though quenching and photooxidation mechanisms. Passive protection, based on the application of barrier materials for packaging, sealing, or encapsulation of the active substances, which prevent oxygen molecules from penetration and physical contact with excited states and active protection, based on the application of oxygen scavenging species are compared. Efficiencies of different approaches together with examples and prospects of their applications are outlined.

Search for top squark pair production in pp collisions at sqrt(s)=13 TeV using single lepton events

Abstract: A search for top squark pair production in pp collisions at root s = 13 TeV is performed using events with a single isolated electron or muon, jets, and a large transverse momentum imbalance. The results are based on data collected in 2016 with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1). No significant excess of events is observed above the expectation from standard model processes. Exclusion limits are set in the context of supersymmetric models of pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. Depending on the details of the model, we exclude top squarks with masses as high as 1120 GeV. Detailed information is also provided to facilitate theoretical interpretations in other scenarios of physics beyond the standard model.