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

The cosmic-ray fluxes of electrons and positrons (e±) are measured with high precision by the space-borne particle spectrometer AMS-02. To infer a precise interpretation of the production processes for e± 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 π± and K± 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 μ± 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 dσ/dTe±(p+p→e±+X) is predicted from 10 MeV up to 10 TeV of e± 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± 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.