High-energy electron observations by PPB-BETS flight in Antarctica

TL;DR

This study reports on the measurement of cosmic-ray electrons between 10 and 800 GeV using a balloon-borne detector in Antarctica, including the first analysis of electron arrival directions above 100 GeV, confirming isotropy.

Contribution

It presents the first measurement of cosmic-ray electron arrival directions above 100 GeV and demonstrates a successful long-duration balloon observation with advanced telemetry and detection systems.

Findings

Electron spectrum from 100 to 800 GeV derived

Electron arrival directions above 100 GeV are isotropic

Successful operation of new telemetry system during flight

Abstract

We have observed cosmic-ray electrons from 10 GeV to 800 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an average altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates with 9 radiation lengths. The performance of the detector has been confirmed by the CERN-SPS beam test and also investigated by Monte-Carlo simulations. New telemetry system using a commercial satellite of Iridium, power supply by solar batteries, and automatic level control using CPU have successfully been developed and operated during the flight. From the long duration balloon observations, we derived the energy spectrum of cosmic-ray electrons in the energy range from 100 GeV to 800 GeV. In addition, for the first time we derived the electron arrival directions above 100 GeV, which is consistent with the isotropic distribution.