Volume 501 - 39th International Cosmic Ray Conference (ICRC2025) - Cosmic-Ray Direct & Acceleration
Measurement of Cr and Ti fluxes and sub-iron/iron flux ratios with CALET on the International Space Station
F. Stolzi*, C. Checchia, Y. Akaike  on behalf of the CALET Collaboration
*: corresponding author
Full text: pdf
Pre-published on: September 23, 2025
Published on: December 30, 2025
Abstract
The analysis of cosmic ray nuclei provides critical insights for a theoretical understanding of the
acceleration and propagation mechanisms of charged particles in our Galaxy. A unique source of
information on the average path length that cosmic rays travel before reaching Earth can be provided
by the elements lying just below iron in the periodic table (sub-iron). Most of these elements are
believed to be produced by the spallation of heavier nuclei as they propagate in the interstellar
medium. The Calorimetric Electron Telescope (CALET), which has been operational on the
International Space Station since 2015, has collected a substantial dataset comprising cosmic-ray
(CR) iron and sub-iron events across a broad energy spectrum. In this contribution we present the
measurements of the energy dependence of the titanium and chromium fluxes in cosmic rays, as
their flux ratios to iron, in the energy interval from 10 GeV/n to 250 GeV/n. The measurements,
based on data collected during eight years of operation, are reported with significantly enhanced
precision compared to existing measurements, including a detailed assessment of systematic
uncertainties. In addition to the sub-iron fluxes, an update of CALET’s analysis of the iron flux
has been carried out up to 1.6 TeV/n.
DOI: https://doi.org/10.22323/1.501.0136
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