Galactic halo size in the light of recent AMS-02 data
Abstract
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. We set constraints on L from Be/B and 10Be/Be data, and we performed a consistency check with positron data. We detail the dependence of Be/B and 10Be/Be on L and forecast on which energy range better data would be helpful for future L improvements. We used USINE v3.5 for the propagation of nuclei, and e+ were calculated with the pinching method of Boudaud et al. (2017). The current AMS-02 Be/B (3\% precision) and ACE-CRIS 10Be/Be ( 10\% precision) data bring similar and consistent constraints on L. The AMS-02 Be/B data alone constrain L=5+3-2~kpc 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 on 10Be/9Be anywhere below 10 GV to further constrain L. Forthcoming AMS-02, HELIX, and PAMELA 10Be/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.