Implications of current nuclear cross sections on secondary cosmic rays with the upcoming DRAGON2 code

Abstract

Current measurements of cosmic-ray fluxes have reached unprecedented accuracy thanks to the new generation of experiments, and in particular the AMS-02 mission. At the same time, significant progress has been made in the propagation models of galactic cosmic rays. These models include several propagation parameters, which are usually inferred from the ratios of secondary to primary cosmic rays, and which depend on the cross sections describing the collisions among the various species of cosmic-ray nuclei. At present, our knowledge of these cross sections in the energy range where cosmic-ray interactions occur is limited, and this is a source of uncertainties in the predicted fluxes of secondary cosmic-ray nuclei. In this work we study the impact of the cross section uncertainties on the fluxes of light secondary nuclei (Li, Be, B) using a preliminary version of the upcoming DRAGON2 code. We first present a detailed comparison of the secondary fluxes computed by implementing different parameterizations for the network of spallation cross sections. Then, we discuss the use of secondary-over-secondary cosmic-ray flux ratios as a tool to improve the consistency of cross sections parameterizations and give insight of the overall uncertainties coming from the cross sections parametrisations. We show that the uncertainties inferred from the cross section data are enough to explain the discrepancies in the Be and Li fluxes with respect to the AMS-02 data, with no need of a primary component in their spectra. In addition, we show that the fluxes of B, Be and Li can be simultaneously reproduced by rescaling their cross sections within the experimental uncertainty. Finally, we also revisit the diffusive estimation of the halo size, obtaining good agreement with previous works and a best fit value of 6.8 ± 1 kpc from the most updated cross sections parametrisations.

Beryllium Radioactive Isotopes as a Probe to Measure the Residence Time of Cosmic Rays in the Galaxy and Halo Thickness: A “Data-Driven” Approach

“…It is important to mention that with 10 B being the daughter nucleus of 10 Be β-decay, it is possible to extract information of the parameters H and D by using the precise measurement of the elemental ratio Be/B in place of the much more difficult measurement of the 10 Be/ 9 Be isotopic ratio. This possibility was originally discussed in [6], and more recently, the expected value of the 10 Be/ 9 Be isotopic ratio in cosmic rays has become able to be inferred from the precisely measured cosmic rays elemental ratios [1,2,4,5]. However, the problem of uncertainties or biases in fragmentation cross-sections should also be mentioned; in particular, nuclear uncertainties in secondary production models are a major limitation in the interpretation of secondary cosmic ray nuclei [5,7,8].…”

“…This possibility was originally discussed in [6], and more recently, the expected value of the 10 Be/ 9 Be isotopic ratio in cosmic rays has become able to be inferred from the precisely measured cosmic rays elemental ratios [1,2,4,5]. However, the problem of uncertainties or biases in fragmentation cross-sections should also be mentioned; in particular, nuclear uncertainties in secondary production models are a major limitation in the interpretation of secondary cosmic ray nuclei [5,7,8]. Thus, isotopically resolved cosmic ray measurements such as the 10 Be/ 9 Be ratio remain very important to model the propagation of cosmic rays.…”

“…Profiting from the fact that the ghost-templates are placed beyond T 10 and that we know 7 Be > 9 Be > 10 Be, the contribution of ghost-templates to Equation ( 4) is small and T 7 can be iteratively evaluated from measured data by using Equation (5).…”

“…The uncertainties of D and H parameters (the latter is known to be in the 3-8 kpc range) also reflect on the accuracy of the determination of secondary anti-proton and positrons fluxes that are the background for the dark matter or exotic (astro-)physics searches [2][3][4][5].…”

A Data Driven Approach to the Measurement of 10Be/9Be in Cosmic Rays with Magnetic Spectrometers

“…The uncertainties on D and H parameters (this last one is know to be in the range 3-8 kpc) also reflects on the accuracy of the determination of secondary anti-proton and positrons fluxes that are the background for the Dark Matter or exotic (astro-)physics searches [2][3][4][5].…”