CTA and SWGO can Discover Higgsino Dark Matter Annihilation

TL;DR

This paper demonstrates that upcoming gamma-ray observatories CTA and SWGO could detect gamma-ray signals from higgsino dark matter annihilation in the Galactic Center, providing a promising test for this dark matter candidate.

Contribution

It presents the most sensitive search to date for gamma-ray lines from higgsino annihilation and assesses the detection prospects with future observatories, incorporating recent cosmological simulations.

Findings

CTA and SWGO can detect higgsino signals for most DM profiles.

Fermi-LAT data is close to detecting higgsino annihilation with 15 years of observations.

H.E.S.S. data excludes the wino model at over twice the expected cross-section.

Abstract

Thermal higgsino dark matter (DM), with a mass near 1.1 TeV, is one of the most well-motivated and untested DM candidates. Leveraging recent hydrodynamic cosmological simulations that give DM density profiles in Milky Way analogue galaxies we show that the line-like gamma-ray signal predicted from higgsino annihilation in the Galactic Center could be detected at high significance with the upcoming Cherenkov Telescope Array (CTA) and Southern Wide-field Gamma-ray Observatory (SWGO) for all but the most pessimistic DM profiles. We perform the most sensitive search to-date for the line-like signal using 15 years of data from the Fermi Large Area Telescope, coming within an order one factor of the necessary sensitivity to detect the higgsino for some Milky Way analogue DM density profiles. We show that H.E.S.S. has sub-leading sensitivity relative to Fermi for the higgsino at present. In contrast, we analyze H.E.S.S. inner Galaxy data for the thermal wino model with a mass near 2.8 TeV; we find no evidence for a DM signal and exclude the wino by over a factor of two in cross-section for all DM profiles considered. In the process, we identify and attempt to correct what appears to be an inconsistency in previous H.E.S.S. inner Galaxy analyses for DM annihilation related to the analysis effective area, which may weaken the DM cross-section sensitivity claimed in those works by around an order of magnitude.