Interpretations of the cosmic ray secondary-to-primary ratios measured by DAMPE

TL;DR

This paper analyzes DAMPE's precise measurements of cosmic ray secondary-to-primary ratios, evaluating various models of cosmic ray production and propagation, and finds that some models require modifications to fully explain the observed spectral hardenings.

Contribution

It systematically compares different cosmic ray models against DAMPE data, highlighting the limitations of re-acceleration models and the need for spectral breaks in diffusion coefficients.

Findings

Re-acceleration models cannot fully reproduce the spectral hardenings.

Models with source secondary production tend to over-predict high-energy antiprotons.

All models show a high-energy positron excess.

Abstract

Precise measurements of the boron-to-carbon and boron-to-oxygen ratios by DAMPE show clear hardenings around $100$ GeV/n, which provide important implications on the production, propagation, and interaction of Galactic cosmic rays. In this work we investigate a number of models proposed in literature in light of the DAMPE findings. These models can roughly be classified into two classes, driven by propagation effects or by source ones. Among these models discussed, we find that the re-acceleration of cosmic rays, during their propagation, by random magnetohydrodynamic waves may not reproduce sufficient hardenings of B/C and B/O, and an additional spectral break of the diffusion coefficient is required. The other models can properly explain the hardenings of the ratios. However, depending on simplifications assumed, the models differ in their quality in reproducing the data in a wide energy range. The models with significant re-acceleration effect will under-predict low-energy antiprotons but over-predict low-energy positrons, and the models with secondary production at sources over-predict high-energy antiprotons. For all models high-energy positron excess exists.