Speaker
Description
Title:
Explaining the Measured Cosmic-Ray Nuclei Spectra with a Dual Source-category Model
Abstract:
Preliminary results shown by the CALET (Calorimetric Electron Telescope) collaboration at the ICRC2025 conference [P. Brogi et al. POS(ICRC2025)019] indicate a break in the proton-helium ratio in the TeV energy range. Assuming cosmic-ray acceleration and propagation mechanisms to be independent of the species, this break could indicate that two cosmic-ray source categories exist, with different helium abundance and different spectral indices and/or cut-off rigidities. These could be different stages in supernova-remnant (SNR) evolution, or SNRs of different star types, with Wolf-Rayet stars being a possible helium-rich source.
This two source-model has been implemented in the numerical cosmic-ray propagation calculation code DRAGON, and the associated input parameter space explored to find source and propagation parameters, which give the best fit to measured nuclei spectra and primary to secondary ratios.
It is shown that such a model with a common source power-law index for all nuclei, but different helium abundance for the two source components, can explain both the break in the proton-helium ratio and the harder index of the measured helium spectrum compared to that of protons and other nuclei, while within experimental uncertainty matching various spectra and ratio measurements by CALET, AMS-02 (Alpha Magnetic Spectrometer) and other experiments.
In addition to discussing this result and the implications of the found best-fit propagation conditions, the machine-learning based methods to explore the model's parameters space will be presented.
