New determination of the production cross section for secondary positrons and electrons in the Galaxy

TL;DR

This paper provides a new, precise analytical model for the production cross sections of secondary positrons and electrons in the Galaxy, significantly improving the accuracy of cosmic-ray propagation interpretations.

Contribution

It introduces new analytical functions for Lorentz invariant cross sections based on collider data, reducing uncertainties in secondary electron and positron production models.

Findings

Predicted differential cross sections with 5-7% uncertainty up to 10 TeV.

Reduced theoretical uncertainties in secondary $e^\u00b1$ flux predictions.

Provided numerical tables and scripts for community use.

Abstract

The cosmic-ray fluxes of electrons and positrons ($e^{\pm}$) are measured with high precision by the space-borne particle spectrometer AMS-02. To infer a precise interpretation of the production processes for $e^{\pm}$ in our Galaxy, it is necessary to have an accurate description of the secondary component, produced by the interaction of cosmic-ray proton and helium with the interstellar medium atoms. We determine new analytical functions of the Lorentz invariant cross section for the production of $\pi^\pm$ and $K^\pm$ by fitting data from collider experiments. We also evaluate the invariant cross sections for several other channels, involving for example hyperon decays, contributing at the few \% level on the total cross section. For all these particles, the relevant 2 and 3 body decay channels are implemented, with the polarized $\mu^\pm$ decay computed with next-to-leading order corrections. The cross section for scattering of nuclei heavier than protons is modeled by fitting data on $p+C$ collisions. The total differential cross section $d\sigma/dT_{e^\pm}(p+p\rightarrow e^\pm+X)$ is predicted from 10 MeV up to 10 TeV of $e^\pm$ energy with an uncertainty of about 5-7\% in the energies relevant for AMS-02 positron flux, thus dramatically reducing the precision of the theoretical model with respect to the state of the art. Finally, we provide a prediction for the secondary Galactic $e^\pm$ source spectrum with an uncertainty of the same level. As a service for the scientific community, we provide numerical tables and a script to calculate energy-differential cross sections.