12-20 July 2017
BEXCO
Asia/Seoul timezone
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Contribution

BEXCO - Room A(101/102)

[CRD039] Analysis and Preliminary Results for the Cosmic Ray Electron Spectrum from CALET

Speakers

  • Yoichi ASAOKA

Primary authors

Description

CALET (CALorimetric Electron Telescope) Mission was launched to the International Space Station (ISS) in August 2015 and has been accumulating scientific data since October 2015. The CALET detector features a very thick calorimeter of 30 radiation-lengths which consists of imaging and total absorption calorimeters (IMC and TASC respectively). Due to its high energy resolution and its ability to discriminate electrons from hadrons, CALET enables a detailed search for various spectral structures in high-energy electron cosmic rays, perhaps providing the first experimental evidence of the presence of a nearby astrophysical cosmic-ray source. Electron spectrum analysis starts with detailed detector calibrations ranging from detector alignment to energy determination, followed by electron event selection and flux normalization. In the first stage of event reduction, well reconstructed shower events fully contained in the fiducial volume were selected. Then, single charged particles were selected using energy deposits in the charge detector. Finally, electron separation from the more abundant protons was done using shower concentration along the shower axis in the bottom layer of IMC, longitudinal and lateral shower development in TASC, and likelihood analysis based on energy deposit distributions in the IMC and TASC layers. The geometrical acceptance and selection efficiencies were calculated using the detailed Monte Carlo simulation of the CALET flight model in which all the relevant detector responses were taken into account. Background contamination due to remaining protons was also estimated and subtracted from the surviving events using simulated proton data which reproduces current observation results. Various consistency checks between data and MC simulation were performed using flight data. A preliminary spectrum of total electrons (electrons + positrons) was obtained in an energy range from 20 GeV to a few TeV. In this contribution, we present the preliminary electron spectrum measured by CALET and discuss the detector calibrations and detailed data analysis.