HIGH ENERGY COSMIC-RAY PROTONS AND HELIUM

Abstract

The work is done within the framework of the PAMELA project [1]. The PAMELA is a space experiment for study of charged particles in the cosmic radiation that has been performed since the launch June 15 2006. This work is dedicated to the high energy cosmic ray proton and helium flux determination (an energy region from 50 GeV/nucleon) based on using a sampling electromagnetic calorimeter. The energy estimation was built on a measurement of a total deposited energy in the calorimeter and an applying of certain event selection criteria connected with an electromagnetic component of a hadronic shower. The helium-proton separation was performed by scintillation detectors of the PAMELA Time of Flight system. This method is indispensable to widen a measurable energy range and to receive additional information in the PAMELA experiment. The obtained energy spectra of protons and helium are presented. 1. Primary Cosmic-ray Helium and Proton Spectra Helium nuclei and Protons are the most abundant elements in cosmic rays. The primary cosmic-ray proton and helium spectrum knowledge is very important to understand the fundamental phenomena of cosmic ray physics. They include cosmic rays acceleration mechanisms, particle propagation, cosmic ray origin and the matter distribution in interstellar space. In addition the proton and helium fluxes contain an essential part of information to be known for a neutrinos absolute flux calculation for example in the movement a neutrino oscillations analysis. The energy range between 1TeV up to 10 TeV remains the most scantily explored one for cosmic ray protons and helium till now. There have been very few measurements for the high energy protons and helium spectra in previous time in balloon borne or satellite experiments, beginning from the PROTON satellites [2] till CREAM [3], but some questions have kept so yet.