Relativistic runaway electron breakdown and Terrestrial Gamma ray Flashes: GEANT4 simulation

Numerical simulation of a relativistic runaway electron breakdown in the upper atmosphere is performed using GEANT4 simulation toolkit. General features of a relativistic runaway electron avalanche are reconstructed and properties of radiations accompanying breakdown are obtained. It is demonstrated dependance of the high energy branch of photon spectra with respect to an altitude and shown what at the reasonable parameters hard photons have spectral index close to the observed value.Comment: 17 pages, 9 figure

Study of Scintillator Strip with Wavelength Shifting Fiber and Silicon Photomultiplier

The performance of the $200\times2.5\times1$ cm$^3$ plastic scintillator strip with wavelength shifting fiber read-out by two novel photodetectors called Silicon PhotoMultipliers (SiPMs) is discussed. The advantages of SiPM relative to the traditional multichannel photomultiplier are shown. Light yield and light attenuation measurements are presented. This technique can be used in muon or calorimeter systems.Comment: 9 pages, 5 figure

Совершенствование транспортного обслуживания в городе Брянске

The object of the study of the article is the passenger transport network of the city of Bryansk. The task of improving transport services for the population is solved in the context of modernising vehicle fleet, transport infrastructure and in-depth implementation of digital technologies. The analytical method allowed to assess the state of the transport system of the city of Bryansk. The assessment touched upon several interrelated areas that provide a high quality of transport services. The data were obtained by studying open Internet resources, including the website of the administration of the city of Bryansk, and through field observations.Work on updating the fleet of route vehicles is carried out within the framework of the «Concept for development of public transport in the city of Bryansk for the period 2015–2025», which over the past four years has led to a significant renewal of the bus fleet of medium and large capacity and to the decrease in the share of buses of small capacity. The road network has also been significantly upgraded.The routes of urban passenger transport have been analysed from the point of view of the degree of duplication. Guidelines for improving the routes of the transport network are proposed.Объектом исследования статьи является пассажирская транспортная сеть города Брянска. Совершенствование транспортного обслуживания населения решается в разрезе модернизации средств транспорта, транспортной инфраструктуры и углубленного внедрения цифровых технологий. На основе аналитического метода проведена оценка состояния транспортного комплекса города Брянска, включающая в себя несколько взаимосвязанных направлений, обеспечивающих высокое качество транспортного обслуживания. Данные получены путём исследования открытых интернет-ресурсов, в том числе интернет-сайта администрации г. Брянска, натурных наблюдений.Работы по обновлению парка маршрутных транспортных средств производятся в рамках «Концепции развития транспорта общего пользования города Брянска на период 2015–2025 годы», что привело за последние четыре года к существенному обновлению автобусного парка средней и большой вместимости и снижению доли автобусов малой вместимости. Также существенно модернизирована дорожная сеть.Проанализированы с точки зрения степени дублирования маршруты городского пассажирского транспорта. Предложены направления совершенствования маршрутов транспортной сети

Meson vacuum phenomenology in a three-flavor linear sigma model with (axial-)vector mesons

We study scalar, pseudoscalar, vector, and axial-vector mesons with non-strange and strange quantum numbers in the framework of a linear sigma model with global chiral $U(N_f)_L \times U(N_f)_R$ symmetry. We perform a global fit of meson masses, decay widths, as well as decay amplitudes. The quality of the fit is, for a hadronic model that does not consider isospin-breaking effects, surprisingly good. We also investigate the question whether the scalar $\bar{q}q$ states lie below or above 1 GeV and find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states. Additionally, we also describe the axial-vector resonances as $\bar{q}q$ states.Comment: 29 pages, 4 figures, 3 tables. v2 is the updated version after referee remarks (dilaton field discussed, a new figure added

Some results of test beam studies of Transition Radiation Detector prototypes at CERN

Operating conditions and challenging demands of present and future accelerator experiments result in new requirements on detector systems. There are many ongoing activities aimed to develop new technologies and to improve the properties of detectors based on existing technologies. Our work is dedicated to development of Transition Radiation Detectors (TRD) suitable for different applications. In this paper results obtained in beam tests at SPS accelerator at CERN with the TRD prototype based on straw technology are presented. TRD performance was studied as a function of thickness of the transition radiation radiator and working gas mixture pressure

Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS

We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_\mu-2 anomaly.Comment: 6 pages, 3 figures; Typos corrected, references adde

Fast photoprocesses in a symmetric indotricarbocyanine dye (hitc) in solutions

Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S0 → S1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals