Combined analysis of AMS02 (Li,Be,B)/C, N/O, ^{3}He, and ^{4}He data
Abstract
Context. The Alpha Magnetic Spectrometer (AMS02) measured several secondarytoprimary ratios enabling a detailed study of Galactic cosmicray transport.
Aims: We constrain previously derived benchmark scenarios (based on AMS02 B/C data only) using other secondarytoprimary ratios to test the universality of transport and the presence of a lowrigidity diffusion break.
Methods: We use the 1D thin disc/thick halo propagation model of USINE V3.5 and a χ^{2} minimisation accounting for a covariance matrix of errors (AMS02 systematics) and nuisance parameters (crosssections and solar modulation uncertainties).
Results: The combined analysis of AMS02 Li/C, Be/C, and B/C strengthens the case for a diffusion slope of δ = 0.50 ± 0.03 with a lowrigidity break or upturn of the diffusion coefficient at GV rigidities. Our simple model can successfully reproduce all considered data (Li/C, Be/C, B/C, N/O, and ^{3}He/^{4}He), although several issues remain: (i) the quantitative agreement depends on the assumptions made on the poorly constrained correlation lengths of AMS02 data systematics; (ii) combined analyses are very sensitive to production crosssections, and we find postfit values differing by ∼5  15% from their most likely values (roughly within currently estimated nuclear uncertainties); (iii) two very distinct regions of the parameter space remain viable, either with reacceleration and convection, or with purely diffusive transport.
Conclusions: To take full benefit of combined analyses of AMS02 data, better nuclear data and a better handle on energy correlations in the data systematic are required. AMS02 data on heavier species are eagerly awaited to explore cosmicray propagation scenarios further.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 July 2020
 DOI:
 10.1051/00046361/202037875
 arXiv:
 arXiv:2002.11406
 Bibcode:
 2020A&A...639A.131W
 Keywords:

 astroparticle physics;
 cosmic rays;
 Astrophysics  High Energy Astrophysical Phenomena;
 High Energy Physics  Phenomenology
 EPrint:
 20 pages, 19 figures, 2 tables