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

Understand

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.