Impact of the spectral hardening of TeV cosmic rays on the prediction of the secondary positron flux

TL;DR

This paper examines how spectral hardening in cosmic-ray protons and helium affects secondary positron flux predictions, revealing a significant increase at high energies, which impacts interpretations of positron sources.

Contribution

It introduces the impact of recent spectral hardening observations on secondary positron flux models and provides fitting formulas for practical use.

Findings

Secondary positron flux increases by up to 60% above 100 GeV due to spectral hardening.

Spectral hardening significantly influences positron flux predictions at high energies.

Results aid in constraining primary positron sources like pulsars or dark matter.

Abstract

The rise in the cosmic-ray positron fraction measured by the PAMELA satellite is likely due to the presence of astrophysical sources of positrons, e.g. pulsars, on the kpc scale around the Earth. Nevertheless, assessing the properties of these sources from the positron data requires a good knowledge of the secondary positron component generated by the interaction of cosmic rays with the interstellar gas. In this paper, we investigate the impact of the spectral hardening in the cosmic-ray proton and helium fluxes recently reported by the ATIC2 and CREAM balloon experiments, on the predictions of the secondary positron flux. We show that the effect is not negligible, leading to an increase of the secondary positron flux by up to $\sim$60% above $\sim$100 GeV. We provide fitting formulae that allow a straightforward utilization of our results, which can help in deriving constraints on one's favorite primary positron source, e.g. pulsars or dark matter.