Indications for a high-rigidity break in the cosmic-ray diffusion coefficient

Abstract

Using cosmic-ray boron to carbon ratio (B/C) data recently released by the AMS-02 experiment, we find tantalizing indications ({\it decisive evidence}, in Bayesian terms) in favor of a diffusive origin for the broken power-law spectra found in protons ($p$) and helium nuclei (He). The result is robust with respect to currently estimated uncertainties in the cross sections, and in the presence of a small component of primary boron, expected because of spallation at the acceleration site. Reduced errors at high energy as well as further cosmic ray nuclei data (as absolute spectra of C, N, O, Li, Be) may definitively confirm this scenario.

6 pages, 2 figures

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• Effects of reacceleration and source grammage on secondary cosmic rays spectra
• Cosmic-Ray Lithium Production at the Nova Eruption Followed by a Type Ia Supernova
• Non-linear acceleration at supernova remnant shocks and the hardening in the cosmic ray spectrum