A simple determination of the halo size from ¹⁰Be/⁹Be data

¹ LPSC, Université Grenoble Alpes, CNRS/IN2P3, 53 Avenue des Martyrs, 38026 Grenoble, France
e-mail: david.maurin@lpsc.in2p3.fr
² Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands

Received: 14 March 2022
Accepted: 31 July 2022

Abstract

Context. The AMS-02 and HELIX experiments should soon provide ¹⁰Be/⁹Be cosmic-ray data of unprecedented precision.

Aims. We propose an analytical formula to quickly and accurately determine L from these data.

Methods. Our formula is validated against the full calculation performed with the propagation code USINE. We compare the constraints on L set by Be/B and ¹⁰Be/⁹Be, relying on updated sets of production cross-sections.

Results. The best-fit L from AMS-02 Be/B data is shifted from 5 kpc to 3.8 kpc when using the updated cross-sections. We obtained consistent results from the Be/B analysis with USINE, L = 3.8_−1.6^+2.8 kpc (data and cross-section uncertainties), and from the analysis of ¹⁰Be/⁹Be data with the simplified formula, L = 4.7 ± 0.6 (data uncertainties) ±2 (cross-section uncertainties) kpc. The analytical formula indicates that improvements on L thanks to future data will be limited by production cross-section uncertainties, unless either ¹⁰Be/⁹Be measurements are extended up to several tens of GeV/n, or nuclear data for the production of ¹⁰Be and ⁹Be are improved; new data for the production cross section of ¹⁶O into Be isotopes above a few GeV/n are especially desired.