The AMS-02 cosmic ray deuteron flux is consistent with a secondary origin
Abstract
The recent measurements of cosmic ray deuteron fluxes by AMS-02 show that the rigidity dependence of deuterons is similar with that of protons but flatter than He, which has been attributed to the existence of primary deuterons with abundance much higher than that from the Big Bang nucleosynthesis. The requirement of highly deuteron-abundant sources imposes a serious challenge on the modern astrophysics since there is no known process to produce a large amount of deuterons without violating other constraints \citep{1976Natur.263..198E}. In this work we demonstrate that the fragmentation of heavy nuclei up to nickel plays a crucial role in shaping/enhancing the spectrum/flux of the cosmic ray deuterons. Based on the latest cosmic ray data, the predicted secondary fluxes of deuterons and He are found to be reasonably consistent with the AMS-02 measurements and a primary deuteron component is not needed. The observed differences between the spectra of D and He, as well as those between the D/He (D/p) and He/He (He/p) flux ratios, measured in the rigidity space, is probably due to the kinetic-energy-to-rigidity conversion and the solar modulation, given different charge-to-mass ratios of D and He. More precise measurements of the fragmentation cross sections of various nuclei to produce deuterons, tritons, and He in a wide energy range will be very helpful in further testing the secondary origin of cosmic ray deuterons.
Cite
@article{arxiv.2406.19315,
title = {The AMS-02 cosmic ray deuteron flux is consistent with a secondary origin},
author = {Qiang Yuan and Yi-Zhong Fan},
journal= {arXiv preprint arXiv:2406.19315},
year = {2024}
}
Comments
14 pages, 8 figures, and 1 table; published in ApJL