Cosmic-ray propagation with DRAGON2: II. Nuclear interactions with the interstellar gas

TL;DR

This paper details the nuclear interaction models and cross sections in the DRAGON2 code, improving the accuracy of cosmic ray secondary flux predictions, especially for light isotopes and antiparticles, to better understand cosmic ray origins.

Contribution

It introduces a comprehensive nuclear production model in DRAGON2, enhancing the simulation of secondary cosmic ray fluxes and isotopic compositions with new fitting procedures and detailed decay networks.

Findings

Developed a new secondary production model for Li, Be, B isotopes.

Compared different models for secondary antiparticles, providing quantitative insights.

Enhanced accuracy in predicting cosmic ray fluxes above 1 GeV/n.

Abstract

Understanding the isotopic composition of cosmic rays (CRs) observed near Earth represents a milestone towards the identification of their origin. Local fluxes contain all the known stable and long-lived isotopes, reflecting the complex history of primaries and secondaries as they traverse the interstellar medium. For that reason, a numerical code which aims at describing the CR transport in the Galaxy must unavoidably rely on accurate modelling of the production of secondary particles. In this work we provide a detailed description of the nuclear cross sections and decay network as implemented in the forthcoming release of the galactic propagation code DRAGON2. We present the secondary production models implemented in the code and we apply the different prescriptions to compute quantities of interest to interpret local CR fluxes (e.g., nuclear fragmentation timescales, secondary and tertiary source terms). In particular, we develop a nuclear secondary production model aimed at accurately computing the light secondary fluxes (namely: Li, Be, B) above 1 GeV/n. This result is achieved by fitting existing empirical or semi-empirical formalisms to a large sample of measurements in the energy range 100 MeV/n to 100 GeV/n and by considering the contribution of the most relevant decaying isotopes up to iron. Concerning secondary antiparticles (positrons and antiprotons), we describe a collection of models taken from the literature, and provide a detailed quantitative comparison.