Extended Measurement of Cosmic-Ray Electron and Positron Spectrum from CALET on the ISS

Abstract

The CALET (CALorimetric Electron Telescope), launched to the International Space Station (ISS) on August 19, 2015 and accumulating scientific data since October 13, 2015, is an all-calorimetric instrument with total vertical thickness of 30 radiation lengths and fine imaging capability, optimized for a measurement of the electron and positron (all-electron) spectrum well into the TeV energy region. CALET will allow for the detailed search for various spectral structures of high-energy all-electron cosmic rays, perhaps providing the first experimental evidence of the presence of a nearby astrophysical cosmic-ray source.

All-electron spectrum analysis starts with detailed detector calibrations covering from detector alignment to energy determination, followed by electron event selection and flux normalization. Special care was taken to identify electrons in the presence of a large hadron background. Possible source of systematic errors are carefully surveyed, and associated uncertainties are estimated for each contribution. As a result, all-electron spectrum is obtained including the TeV energy range.

In this contribution, we will present the all-electron spectrum measured by CALET and compare it with those obtained by other experiments.