Bremsstrahlung signatures of dark matter annihilation in the Sun

TL;DR

This paper investigates how bremsstrahlung processes in dark matter annihilation within the Sun can produce detectable neutrino signals, relaxing previous suppression effects and enhancing detection prospects at IceCube/DeepCore.

Contribution

It provides a detailed evaluation of neutrino spectra from bremsstrahlung channels and proposes methods to combine sensitivities across multiple channels for dark matter detection.

Findings

Bremsstrahlung channels relax chirality suppression in dark matter annihilation.

Neutrino spectra from these channels are calculated including spin and helicity effects.

Strategies for combining sensitivities across channels improve detection prospects.

Abstract

The nonrelativistic annihilation of Majorana dark matter in the Sun to a pair of light fermions is chirality-suppressed. Annihilation to 3-body final states $\ell^+f^-V$, where $V=W,Z,\gamma$, and $\ell$ and $f$ are light fermions (that may be the same), becomes dominant since bremsstrahlung relaxes the chirality suppression. We evaluate the neutrino spectra at the source, including spin and helicity dependent effects, and assess the detectability of each significant bremsstrahlung channel at IceCube/DeepCore. We also show how to combine the sensitivities to the dark matter-nucleon scattering cross section in individual channels, since typically several channels contribute in models.