Galactic halo size in the light of recent AMS-02 data

N Weinrich,Y Génolini,J Lavalle,G Weymann-Despres,L Derome,P Salati,D Maurin,P Serpico,M Boudaud

doi:10.1051/0004-6361/202038064

Abstract

Context.The vertical diffusive halo size of the Galaxy,L, is a key parameter for dark matter indirect searches. It can be better determined thanks to recent AMS-02 data.Aims.We set constraints onLfrom Be/B and10Be/Be data, and we performed a consistency check with positron data. We detail the dependence of Be/B and10Be/Be onLand forecast on which energy range better data would be helpful for futureLimprovements.Methods.We usedUSINE V3.5for the propagation of nuclei, and e+were calculated with the pinching method.Results.The current AMS-02 Be/B (∼3% precision) and ACE-CRIS10Be/Be (∼10% precision) data bring similar and consistent constraints onL. The AMS-02 Be/B data alone constrainL= 5−2+3kpc at a 68% confidence level (spanning different benchmark transport configurations), a range for which most models do not overproduce positrons. Future experiments need to deliver percent-level accuracy on10Be/9Be anywhere below 10 GV to further constrainL.Conclusions.Forthcoming AMS-02, HELIX, and PAMELA10Be/9Be results will further test and possibly tighten the limits derived here. Elemental ratios involving radioactive species with different lifetimes (e.g. Al/Mg and Cl/Ar) are also awaited to provide complementary and robuster constraints.

Highlights

Finding the Galactic cosmic-ray (CR) sources, solving the details of CR transport in the Galaxy, and using the CR as a channel to identify the nature of dark matter (DM) are among the main challenges in CR physics
Using updated cross sections and propagating their uncertainties, we find here L = 5+−32 kpc based on AMS-02 Be/B data, which is compatible with values derived from ACE-CRIS 10Be/9Be data
In the context of recent high-precision AMS-02 data, we have revisited the constraints set on the halo size of the Galaxy from radioactive species and positron fluxes

Summary

Introduction

Finding the Galactic cosmic-ray (CR) sources, solving the details of CR transport in the Galaxy, and using the CR as a channel to identify the nature of dark matter (DM) are among the main challenges in CR physics. DM interpretations for antimatter CRs depend on both the transport and geometry parameters (Donato et al 2004; Delahaye et al 2008; Aramaki et al 2016); the latter is mostly determined via CR radioactive clocks. These clocks have a lifetime of approximately a million years, one order of magnitude shorter than the typical CR propagation time in the Galaxy.

Results

Discussion

Conclusion