Interpretation of AMS-02 beryllium isotope fluxes using data-driven production cross sections

The beryllium isotopic fluxes are measured up to 12 GeV/n energies by the AMS-02 Collaboration with unprecedented precision. As secondary cosmic rays (CRs), the Be isotopes include both stable and unstable species, which are crucial for constraining the propagation parameters of the Galactic CRs. However, when constraining the Galactic propagation parameters it shows inconsistency by using ¹⁰Be/⁹Be and by using Be/B data. We attribute this mainly to the uncertainties of the ⁹Be production cross section, while the ⁷Be and ¹⁰Be have much better cross section measurements. Therefore, we employ ¹⁰Be and ⁷Be, instead of ⁹Be, to constrain the propagation parameters. We parametrize the cross sections that utilize all the available experimental data. The propagation parameters are well-constrained, with the diffusion halo thickness at 5.67±0.76 kpc, representing a moderate value compared to previous analogous works. Combining the well-constrained CR propagation model and the recent measurements of ⁹Be flux, we conversely constrain the major production cross section of ⁹Be and find that it ought to be remarkably lower than previously thought. With the revised ⁹Be production cross section the predicted Be/B ratio by the propagation model is now consistent with the measurement of AMS-02. It should be noted that with the unprecedented precision of the CR data measured by AMS-02 the CR data are potentially used to check the nucleon production cross sections, as shown in the present work.