Observation of Protons and Light Nuclei with CALET: Analysis and Preliminary Results

Abstract

The CALorimetric Electron Telescope (CALET) has been collecting science data on the JEM-EF external platform of the ISS since mid-October 2015. To date, more than 300 million triggers generated by high-energy charged particles and photons from space have been recorded. The instrument includes a two-layered Charge Detector (CHD) equipped with segmented scintillators to identify - via a measurement of their electric charge - individual elements from proton to iron and to detect trans-iron nuclei. Complementary charge and tracking information is provided by the electromagnetic Imaging Calorimeter (IMC), instrumented with individually read-out scintillating fibers, and followed by a thick homogeneous calorimeter (TASC). The whole calorimetric system provides an excellent energy and angular resolution and electron/proton discrimination of order 10−⁵. In addition to its primary goal to explore the electron spectrum in the energy region above 1 TeV, CALET can also study the cosmic-ray hadronic sector by contributing high precision measurements of the energy spectra, relative abundances and secondary-to-primary ratios of elements from proton to iron. Deviations from a simple power-law, as reported by CREAM, PAMELA and AMS-02 in the spectra of light nuclei are under study from a few tens of GeV to the multi-TeV region. In this paper, a progress report on the analysis and preliminary results relative to the observation of protons and light nuclei with CALET will be given. CALET is a space mission of the Japanese Aerospace Agency (JAXA) in collaboration with the Italian Space Agency (ASI) and NASA.