Impact of inhomogeneous diffusion on secondary cosmic ray and antiproton local spectra

TL;DR

This paper explores how spatially-dependent inhomogeneous diffusion of cosmic rays affects the local spectra of secondary cosmic rays and antiprotons, potentially improving agreement with observations and informing dark matter studies.

Contribution

It introduces an inhomogeneous diffusion model for cosmic ray propagation and analyzes its effects on secondary CRs and antiprotons, comparing it with other scenarios.

Findings

Inhomogeneous diffusion improves compatibility with observed antiproton fluxes.

The model predicts a harder antiproton spectrum at high energies.

Dark matter antiproton flux predictions remain largely unaffected.

Abstract

Recent $\gamma$-ray and neutrino observations seem to favor the consideration of non-uniform diffusion of cosmic rays (CRs) throughout the Galaxy. In this study, we investigate the consequences of spatially-dependent inhomogeneous propagation of CRs on the fluxes of secondary CRs and antiprotons detected at Earth. A comparison is made among different scenarios in search of potential features that may guide us toward favoring one over another in the near future. We also examine both the influence of inhomogeneous propagation in the production of secondary CRs from interactions with the gas, and the effects of this scenario on the local fluxes of antiprotons and light antinuclei produced as final products of dark matter annihilation. Our results indicate that the consideration of an inhomogeneous diffusion model could improve the compatibility of the predicted local antiproton flux with that of B, Be and Li, assuming only secondary origin of these particles. In addition, our model predicts a slightly harder local antiproton spectrum, making it more compatible with the high energy measurements of AMS-02. Finally, no significant changes are expected in the predicted local flux of antiprotons and antinuclei produced from dark matter among the different considered propagation scenarios.