Galactic Cosmic Ray Nuclei as a Tool for Astroparticle Physics

TL;DR

The article presents a coherent, semi-analytic diffusion-convection framework to model Galactic CR nuclei propagation (100 MeV/nuc–100 GeV/nuc) within a two-zone cylindrical geometry, incorporating galactic wind, reacceleration, energy losses, and solar modulation. Parameters are tightly constrained by B/C and related data, enabling robust predictions for secondary/primary nuclei, radioactive isotopes, and light antinuclei, and providing a platform to assess exotic signals from SUSY dark matter and PBHs. The work also explores the spatial origins of CRs, the local interstellar medium structure (including the Local Bubble), and how diffusion parameters influence the origin and detectability of exotic primaries in the halo. Overall, the authors connect standard CR propagation with astroparticle physics, outlining how future cross-section measurements and high-precision CR data can sharpen constraints on Galactic structure and new physics.

Abstract

Cosmic Ray nuclei in the energy range 100 MeV/nuc - 100 GeV/nuc provide crucial information about the physical properties of the Galaxy. They can also be used to answer questions related to astroparticle physics. This paper reviews the results obtained in this direction, with a strong bias towards the work done by the authors at {\sc lapth}, {\sc isn} and {\sc iap}. The propagation of these nuclei is studied quantitatively in the framework of a semi-analytical two-zone diffusion model taking into account the effect of galactic wind, diffuse reacceleration and energy losses. The parameters of this model are severely constrained by an analysis of the observed B/C ratio. These constraints are then used to study other species such as radioactive species and light antinuclei. Finally, we focus on the astroparticle subject and we study the flux of antiprotons and antideuterons that might be due to neutralino annihilations or primordial black hole evaporation. The question of the spatial origin of all these species is also addressed.

Figures (36)

• Figure 1: Characteristic times of several processes affecting the propagation of cosmic rays are displayed in the 100 MeV/nuc-100 GeV/nuc energy range. Typical values $K_0=0.03 \; \hbox{kpc}^2 \; \hbox{Myr}^{-1}$, $\delta = 0.6$ and $V_c = 10 \; \hbox{km} \; \hbox{s}^{-1}$ were considered. The dominant process at energies higher than a few GeV is the escape through the boundaries of the diffusive volume. The effect of spallations is seen to be small for the propagation of protons, whereas it is crucial for heavy nuclei such as Fe.
• Figure 2: Schematic view of our Galaxy as well as all propagation steps included in our model.
• Figure 3: Schematic representation (not drawn to scale) between the local bubble and the neighboring Loop I superbubble (from Breitschwerdt).
• Figure 4: Radial distribution of the sources. The thin lines correspond to the p and He component, with the three types (a), (b) and (c) discussed above. The thick lines correspond to the other species, for which the distribution id modified by the metallicity gradient, according to Eq. (\ref{['metallicity_gradient2']}).
• Figure 5: Schematic view of our Galaxy: exotic primary CR production follows either the dark matter profile (PBH, solid line) or the square of the dark matter profile (SUSY, dashed line). They have been arbitrary rescaled.