Antiproton constraints on the GeV gamma-ray excess: a comprehensive analysis

TL;DR

This paper investigates the gamma-ray excess in the Galactic Center, emphasizing the importance of secondary emission calculations and antiproton constraints to evaluate the dark matter interpretation, with results sensitive to propagation and solar modulation uncertainties.

Contribution

It provides an improved computation of secondary emission from dark matter and assesses antiproton constraints considering propagation and solar modulation effects.

Findings

Antiproton constraints strongly limit the dark matter hadronic channel interpretation.

Secondary emission calculations are crucial for understanding the leptonic channel.

Uncertainties in propagation and solar modulation significantly affect constraints.

Abstract

A GeV gamma-ray excess has possibly been individuated in Fermi-LAT data from the Galactic Center and interpreted in terms of Dark Matter (DM) annihilations, either in hadronic (essentially $b\bar{b}$) or leptonic channels. In order to test this tantalizing interpretation, we address two issues: (i) we improve the computation of secondary emission from DM (Inverse Compton and Bremsstrahlung) with respect to previous works, confirming it to be very relevant for determining the DM spectrum in the leptonic channels, so that any conclusion on the DM nature of the signal critically depends on this contribution; (ii) we consider the constraints from antiprotons on the DM hadronic channel, finding that the uncertainties on the propagation model, and in particular on the halo height, play a major role. Moreover, we discuss the role of solar modulation, taking into account possible charge dependent effects whose importance is estimated exploiting detailed numerical tools. The limits that we obtain severely constrain the DM interpretation of the excess in the hadronic channel, for standard assumptions on the Galactic propagation parameters and solar modulation. However, they considerably relax if more conservative choices are adopted.