Strategies of Searches of the Angular Anisotropy of Fluxes of Galactic Electrons and Positrons by Means of the PAMELA Ex
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EMENTARY PARTICLES AND FIELDS Experiment
Strategies of Searches of the Angular Anisotropy of Fluxes of Galactic Electrons and Positrons by Means of the PAMELA Experiment Calorimeter A. V. Karelin1)* and S. A. Voronov1) Received April 9, 2018
Abstract—The possibility of studying the anisotropy of the total fluxes of electrons and positrons of high-energy (10 GeV to 1 TeV) cosmic rays in the PAMELA satellite-borne experiment by means of a calorimeter is considered. The procedure developed with aim of performing searches for this anisotropy is described along with the results of applying it to a test data sample. DOI: 10.1134/S1063778818050071
1. INTRODUCTION The electron component of cosmic rays consists of electrons and positrons. The electrons and positrons of high-energy (Е > 10 GeV) cosmic rays carry valuable information about their nature and about their interaction with interstellar matter and with local magnetic fields in the course of their propagation. High-energy electrons and positrons propagating through interstellar space lose energy primarily via synchrotron radiation in galactic magnetic fields and via inverse Compton scattering off interstellar photons. The energy loss per unit time in these processes is in direct proportion to the square of the electron energy; therefore, electrons and positrons of such energies cannot propagate over long distances from their sources. Measurements of the energy spectra of electrons and positrons in various experiments [1–3] reveal that the intensity of the electron component is about 1% of the intensity of protons at an energy of 10 GeV and decreases faster at higher energies than the intensity of the nuclear component of cosmic rays. The observed total energy spectrum of electrons and positrons in near-Earth space contains the primary and secondary components. The primary electron flux is formed in astrophysical objects, such as pulsars, or is emitted upon supernova explosions. Secondary electrons and positrons are produced in collisions of primary fluxes of cosmic rays—predominantly protons—with an interstellar gas (atomic hydrogen) via the pion-decays processes π ± → μ± → e± and π0 → 2γ → 2e± . 1)
National Research Nuclear University MEPhI, Moscow, 115409 Russia. * E-mail: [email protected]
Among numerous models that describe the propagation of electrons in the Milky Way Galaxy, the diffusion model is generally recognized. The shape of the electron spectrum within this model was obtained in many theoretical studies for various boundary conditions (see, for example, the review article of Ginzburg and Ptuskin [4]). Cosmic rays propagating in the Milky Way Galaxy undergo scattering on random and irregular components of the galactic magnetic field, with the result that the distribution of cosmic rays becomes fully isotropic, but, in the diffusion model and models similar to it, the production of electrons in sources situated near the Solar System may lead to a dipole angular anisotropy in the measured (in nearEarth space) electron and positron fluxes of galactic cosmic ray
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