1,421 research outputs found

    Breaks in interstellar spectra of positrons and electrons derived from time-dependent AMS data

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    Until fairly recently, it was widely accepted that local cosmic ray spectra were largely featureless power laws, containing limited information on their acceleration and transport. This viewpoint is currently being revised in the light of evidence for a variety of spectral breaks in the fluxes of cosmic ray nuclei. Here, we focus on cosmic ray electrons and positrons which at the highest energies must be of local origin due to strong radiative losses. We consider a pure diffusion model for their Galactic transport and determine its free parameters by fitting data in a wide energy range: measurements of the interstellar spectrum by Voyager at MeV energies, radio synchrotron data (sensitive to GeV electrons and positrons) and local observations by AMS up to ~ 1 TeV. For the first time, we also model the time-dependent fluxes of cosmic ray electrons and positrons at GeV energies recently presented by AMS, treating solar modulation in a simple extension of the widely used force-field approximation. We are able to reproduce all the available measurements to date. Our model of the interstellar spectrum of cosmic ray electrons and positrons requires the presence of a number of spectral breaks, both in the source spectra and the diffusion coefficients. While we remain agnostic as to the origin of these spectral breaks, their presence will inform future models of the microphysics of cosmic ray acceleration and transport.Comment: 19 pages, 9 figures; submitted to PR

    Constraints on leptophilic dark matter from the AMS-02 experiment

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    The annihilation of dark matter particles in the galactic halo of the Milky Way may lead to cosmic ray signatures that can be probed by the AMS-02 experiment, which has measured the composition and fluxes of charged cosmic rays with unprecedented precision. Given the absence of characteristic spectral features in the electron and positron fluxes measured by AMS-02, we derive upper limits on the dark matter annihilation cross section for leptophilic dark matter models. Our limits are based on a new background model that describes all recent measurements of the energy spectra of cosmic ray positrons and electrons. For thermal dark matter relics, we can exclude dark matter masses below about 100 GeV. We include the radiation of electroweak gauge bosons in the dark matter annihilation process and compute the antiproton signal that can be expected within leptophilic dark matter models.Comment: 7 pages, 3 figures, 1 table. Matches the published version apart from typo corrected in Eq.

    Monte Carlo Simulations of the Transition Radiation Detector of the AMS-02 Experiment

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    The Transition Radiation Detector of the AMS-02 experiment on the International Space Station is used for the separation of cosmic-ray positrons and electrons from protons and anti-protons, and for the identification of nuclei up to carbon (Z<=6). We present the Geant4 simulation that is used to describe the ionization and transition radiation processes and compare its results to flight data from AMS-02. After applying empirical corrections to the simulated data, the particle energy deposition and likelihood distributions in the TRD are described with high accuracy.Comment: 7 pages, 9 figures. Accepted for publication in Nuclear Inst. and Methods in Physics Research, A. CC-BY-NC-ND 4.0 licens

    Информационная система учета и анализа деятельности магазина по продаже мягкой мебели

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    Объектом исследования является процесс учета и анализа деятельности магазина по продаже мягкой мебели ООО "Сибирская мебельная компания". Цель работы – разработка ИС учета и анализа деятельности магазина по продаже мягкой мебели для ООО "Сибирская мебельная компания". В процессе исследования изучены организационная структура и документооборот ООО "Сибирская мебельная компания". Проведен теоретический анализ предметной области, обзор аналогов разрабатываемой ИС, спроектирована и разработана ИС, проведен анализ вредных факторов на рабочем месте пользователей.The process of accounting and analysis of the LLC "Siberian Furniture Company" furniture store's activities is the object of the study. The purpose of the work is to develop an information system for accounting and analysis of the LLC "Siberian Furniture Company" furniture store's activities. In the course of the study, the organizational structure and document flow of LLC "Siberian Furniture Company" were studied. A theoretical analysis of the subject area, a review of the analogues of the developed information system, an information system is designed and developed, an analysis of harmful factors in the workplace of users is carried out

    Yukawa unification in SO(10) with light sparticle spectrum

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    We investigate supersymmetric SO(10) GUT model with \mu<0. The requirements of top-bottom-tau Yukawa unification, correct radiative electroweak symmetry breaking and agreement with the present experimental data may be met when the soft masses of scalars and gauginos are non-universal. We show how appropriate non-universalities can easily be obtained in the SO(10) GUT broken to the Standard Model. We discuss how values of BR(b-->s \gamma) and (g-2)_\mu simultaneously in a good agreement with the experimental data can be achieved in SO(10) model with \mu<0. In the region of the parameter space preferred by our analysis there are two main mechanisms leading to the LSP relic abundance consistent with the WMAP results. One is the co-annihilation with the stau and the second is the resonant annihilation via exchange of the Z boson or the light Higgs scalar. A very interesting feature of SO(10) models with negative \mu is that they predict relatively light sparticle spectra. Even the heaviest superpartners may easily have masses below 1.5 TeV in contrast to multi-TeV particles typical for models with positive \mu.Comment: 23 pages, 5 figure

    Inverted sfermion mass hierarchy and the Higgs boson mass in the MSSM

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    It is shown that MSSM with first two generations of squarks and sleptons much heavier than the third one naturally predicts the maximal stop mixing as a consequence of the RG evolution, with vanishing (or small) trilinear coupling at the high scale. The Higgs boson is generically heavy, in the vicinity of 125 GeV. In this inverted hierarchy scenario, motivated by the supersymmetric FCNC problem and models for fermion masses based on horizontal symmetries, the mass of the lightest stop is O(0.5) TeV and of gluino - O(2-3) TeV. The LSP can be either higgsino or bino or a mixture of both and it can be a good dark matter candidate.Comment: 22 pages, 8 figures, comments and references adde