A simple determination of the halo size $L$ from $^{10}$Be/$^9$Be data

Maurin, D.; Bueno, E. Ferronato; Derome, L.

doi:10.48550/arxiv.2203.07265

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“…We emphasised that most (and possibly all) previous interpretations of the AMS-02 Li, Be, and B data rely on a cross-section set that does not account for these enhancements. The consequences of using updated cross sections are the following 20 : (i) in the ranking of the most important progenitors for LiBeB, Fe becomes the third most important element, responsible for ∼ 10% of Li and Be 21 , but only ∼ 4% for B; (ii) the combined analysis of the AMS-02 Li/C, Be/C, and B/C ratios lead to a 20% larger value of the diffusion coefficient (compared to those obtained in our previous investigation), which is not without consequences for the predictions made, for instance, on secondary antiprotons (Boudaud et al 2020) 22 ; (iii) the updated cross-section sets also impact the predictions for the isotopic ratios of Li, Be, and B-in particular, uncertainties on the production of Be isotopes may be an issue for the determination of the halo size of the Galaxy (see the companion paper, Maurin et al 2022); (iv) via the inspection of the post-fit values of the nuisance parameters (on the production cross section), we find that the updated cross-section sets, expected to be closer to the truth, indeed provide a more consistent description of the 20 These cross-section sets will appear at some point in the next release of the usine code. They can be obtained on demand in the meantime.…”

Section: Discussionmentioning

confidence: 75%

The importance of Fe fragmentation for LiBeB analyses

Maurin

Bueno

Génolini

et al. 2022

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Context. High-precision data from AMS-02 on Li, Be, and B provide the best constraints on Galactic cosmic-ray transport parameters. Aims. We re-evaluate the impact of Fe fragmentation on the Li, Be, and B modelling. We discuss the consequences on the transport parameter determination and reassess whether a primary source of Li is needed to match AMS-02 data. Methods. We renormalised several cross-section parametrisations to existing data for the most important reactions producing Li, Be, and B. We used the usine code with these new cross-section sets to re-analyse Li/C, Be/C, and B/C AMS-02 data. Results. We built three equally plausible cross-section sets. Compared to the initial cross-section sets, they lead to an average enhanced production of Li (∼ 20 − 50%) and Be (∼ 5 − 15%), while leaving the B flux mostly unchanged. In particular, Fe fragmentation is found to contribute to up to 10% of the Li and Be fluxes. Used in the combined analysis of AMS-02 Li/C, Be/C, and B/C data, the fit is significantly improved, with an enhanced diffusion coefficient (∼ 20%). The three updated cross-section sets are found to either slightly undershoot or overshoot the Li/C and B/C ratios: this strongly disfavours evidence for a primary source of Li in cosmic rays. We stress that isotopic cosmic-ray ratios of Li (and to a lesser extent Be), soon to be released by AMS-02, are also impacted by the use of these updated sets. Conclusions. Almost no nuclear data exist for the production of Li and B isotopes from Ne, Mg, Si, and Fe, whereas these reactions are estimated to account for ∼ 20% of the total production. New nuclear measurements would be appreciated and help to better exploit the high-precision AMS-02 cosmic-ray data.

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Section: Discussionmentioning

confidence: 75%