Dark matter in the solar system II: WIMP annihilation rates in the Sun

TL;DR

This paper refines calculations of WIMP annihilation rates in the Sun, considering gravitational and optical effects, impacting neutrino telescope sensitivity estimates for dark matter detection.

Contribution

It introduces a more accurate model of WIMP annihilation rates in the Sun by including gravitational and optical effects, improving predictions for neutrino telescope observations.

Findings

Annihilation rate estimates decrease due to gravitational and optical effects.

Sensitivity to 100 GeV WIMPs remains unchanged, but for 10 TeV WIMPs it is reduced.

Provides improved guidance for future neutrino telescope experiments.

Abstract

We calculate the annihilation rate of weakly interacting massive particles (WIMPs) in the Sun as a function of their mass and elastic scattering cross section. One byproduct of the annihilation, muon neutrinos, may be observed by the next generation of neutrino telescopes. Previous estimates of the annihilation rate assumed that any WIMPs from the Galactic dark halo that are captured in the Sun by elastic scattering off solar nuclei quickly reach thermal equilibrium in the Sun. We show that the optical depth of the Sun to WIMPs and the gravitational forces from planets both serve to decrease the annihilation rate below these estimates. While we find that the sensitivity of upcoming km^3-scale neutrino telescopes to ~100 GeV WIMPs is virtually unchanged from previous estimates, the sensitivity of these experiments to ~10 TeV WIMPs may be an order of magnitude less than the standard calculations would suggest. The new estimates of the annihilation rates should guide future experiment design and improve the mapping from neutrino event rates to WIMP parameter space.