Positrons from cosmic rays interactions and dark matter annihilations

TL;DR

This paper investigates the origins of cosmic ray positrons, focusing on dark matter annihilation and secondary production, analyzing uncertainties, and assessing the stability of the positron fraction against flux variations.

Contribution

It provides a comprehensive analysis of positron sources, highlighting the impact of propagation uncertainties and flux variations on interpreting cosmic ray positron data.

Findings

Propagation uncertainties dominate the positron flux predictions.

Key features of dark matter annihilation signals are robust despite uncertainties.

Small variations in electron flux can significantly alter the positron fraction.

Abstract

The electron and positron cosmic rays puzzle has triggered a revolution in the field of astroparticle physics. Many hypotheses have been proposed to explain the unexpected rise of the positron fraction, observed by HEAT and PAMELA experiments, for energies larger than few GeVs. In this work, we study sources of positron cosmic rays related to annihilation of dark matter and secondary production. In both cases, we consider the impact of uncertainties related to dark matter physics, nuclear physics and propagation of cosmic rays, finding that the largest uncertainties come from propagation. We find that some key features present in the positron signal from dark matter annihilation are preserved even though the uncertainties. In addition, we study the stability of the positron fraction under small variations of the electron flux, which is usually considered as known, we found that considering just the observational uncertainties in the electron flux is enough to changed dramatically the positron fraction in the energy range were the excess is observed.