Bayesian Analysis of the Hardening in AMS-02 Nuclei Spectra

Based on the precise nuclei data released by AMS-02, we study the spectra hardening of both the primary (proton, helium, carbon, oxygen, and the primary component of nitrogen) and the secondary (anti-proton, lithium, beryllium, boron, and the secondary component of nitrogen) cosmic-ray (CR) nuclei. With the diffusion-reacceleration model, we consider two schemes to reproduce the hardening in the spectra: (i) a high-rigidity break in primary source injection; and (ii) a high-rigidity break in diffusion coefficient. The global fitting results show that both schemes could reproduce the spectra hardening in the current status. More precise multi-TV data (especially the data of secondary CR species) is needed if one wants to distinguish these two schemes. In our global fitting, each of the nuclei species is allocated an independent solar-modulation potential and a rescale factor (which accounts for the isotopic abundance for primary nuclei species and uncertainties of production cross section or inhomogeneity of CR sources and propagation for secondary nuclei species). The fitting values of these two parameter classes show us some hints on some new directions in CR physics. All the fitted rescale factors of primary nuclei species have values that are systematically smaller than 1.0, while that of secondary nuclei species are systematically larger than 1.0. Moreover, both the rescale factor and solar-modulation potential of beryllium have values that are obviously different from other species. This might indicate that beryllium has the specificity not only on its propagation in the heliosphere, but also on its production cross section. All these new results should be seriously studied in the future.