Interpretation of the cosmic ray positron and antiproton fluxes

TL;DR

This paper analyzes cosmic ray positron and antiproton fluxes across 1-350 GeV, showing their spectral shapes and ratios are consistent with secondary production in hadronic interactions, impacting cosmic ray astrophysics.

Contribution

It provides detailed spectral measurements and demonstrates that positrons and antiprotons likely share a common secondary origin, confirming theoretical models of cosmic ray interactions.

Findings

Spectral indices of positrons and antiprotons are approximately equal.

Positron/antiproton flux ratio is constant (~2) above 30 GeV.

Flux ratios at lower energies align with secondary production expectations.

Abstract

The spectral shape of cosmic ray positrons and antiprotons has been accurately measured in the broad kinetic energy range 1-350 GeV. In the higher part of this range (E > 30 GeV) the e+ and pbar are both well described by power laws with spectral indices gamma[e+] = 2.77 +-0.02 and gamma[pbar] = 2.78 +- 0.04 that are approximately equal to each other and to the spectral index of protons. In the same energy range the positron/antiproton flux ratio has the approximately constant value 2.04+-0.04, that is consistent with being equal to the ratio e_/pbar calculated for the conventional mechanism of production, where the antiparticles are created as secondaries in the inelastic interactions of primary cosmic rays with interstellar gas. The positron/antiproton ratio at lower energy is significantly higher (reaching the approximate value e+/pbar = 100 for E around 1 GeV), but in the entire energy range 1-350 GeV, the flux ratio is consistent with being equal to ratio of the production rates in the conventional mechanism, as the production of low energy antiprotons is kinematically suppressed in collisions with a target at rest. These results strongly suggest that cosmic ray positrons and antiprotons have a common origin as secondaries in hadronic interactions. This conclusion has broad implications for the astrophysics of cosmic rays in the Galaxy.