The cosmic-ray electron spectrum measured with the CALorimetric Electron Telescope

Abstract

Direct measurements of cosmic-rays (CRs) are important to understand the sites and the processes of acceleration and propagation of high-energy particles in the interstellar medium. For example, detailed measurements of the high-energy electron+positron (hereafter simply “electron”) spec- trum can provide information about nearby CR sources. The electron spectrum may also exhibit features from Dark Matter (DM) annihilation. The CALorimetric Electron Telescope (CALET) is a Japanese-led international space mission promoted by JAXA (Japan Aerospace Exploration Agency) in collaboration with the Italian Space Agency (ASI) and NASA. The apparatus is con- tinuously operating on board of the International Space Station (ISS) since October 2015. Its main objective is to perform precise direct measurements of the electron cosmic-ray spectrum in the en- ergy region above 1 TeV; other scientific objectives are the measurement of hadron spectra, from proton to iron and above, up to several hundreds of TeV and the detection of gamma-ray emissions up to 10 TeV. The instrument consists of a deep homogeneous calorimeter, a sampling-imaging calorimeter and a charge detector. The electron measurement is characterized by excellent energy resolution (about 1% at 1 TeV) and good proton rejection power (about 10^5 at 1 TeV). We will discuss the current status of the electron data analysis, mainly focusing on the electron/proton discrimination methods. Also, we will present a comparison between electron spectra measured by CALET and other experiments. The current CALET electron measurement will be extended to higher energies in the next years, with the increase of accumulated statistics.