Propagation of H and He cosmic ray isotopes in the Galaxy: astrophysical and nuclear uncertainties

TL;DR

This paper analyzes cosmic ray isotopes to understand their propagation in the Galaxy, comparing AMS-01 data with models, highlighting the importance of nuclear uncertainties, and proposing secondary-to-secondary ratios as consistency tests.

Contribution

It provides a detailed comparison of cosmic ray isotope data with propagation models, emphasizing the role of nuclear uncertainties and proposing new diagnostic ratios.

Findings

AMS-01 data aligns with diffusive-reacceleration models

Nuclear uncertainties limit model reliability more than astrophysical ones

Secondary-to-secondary ratios are effective consistency diagnostics

Abstract

Observations of light isotopes in cosmic rays provide valuable information on their origin and propagation in the Galaxy. Using the data collected by the AMS-01 experiment in the range ~0.2-1.5 GeV/nucleon, we compare the measurements on 1H, 2H, 3He, and 4He with calculations for interstellar propagation and solar modulation. These data are described well by a diffusive-reacceleration model with parameters that match the B/C ratio data, indicating that He and heavier nuclei such as C-N-O experience similar propagation histories. Close comparisons are made within the astrophysical constraints provided by the B/C ratio data and within the nuclear uncertainties arising from errors in the production cross-section data. The astrophysical uncertainties are expected to be dramatically reduced by the data upcoming from AMS-02, so that the nuclear uncertainties will likely represent the most serious limitation on the reliability of the model predictions. On the other hand, we find that secondary-to-secondary ratios such as 2H/3He, 6Li/7Li or 10B/11B are barely sensitive to the key propagation parameters and can represent a useful diagnostic test for the consistency of the calculations.