Probing dark matter self-interaction in the Sun with IceCube-PINGU

Chian-Shu Chen,Fei-Fan Lee,Yen-Hsun Lin,Guey-Lin Lin

doi:10.1088/1475-7516/2014/10/049

Abstract

We study the capture, annihilation and evaporation of dark matter (DM) inside the Sun. It has been shown that the DM self-interaction can increase the DM number inside the Sun. We demonstrate that this enhancement becomes more significant in the regime of small DM mass, given a fixed DM self-interaction cross section. This leads to the enhancement of neutrino flux from DM annihilation. On the other hand, for DM mass as low as as a few GeVs, not only the DM-nuclei scatterings can cause the DM evaporation, DM self-interaction also provides non-negligible contributions to this effect. Consequently, the critical mass for DM evaporation (typically 3 ∼ 4 GeV without the DM self-interaction) can be slightly increased. We discuss the prospect of detecting DM self-interaction in IceCube-PINGU using the annihilation channels χχ → τ+τ-, νν̄ as examples. The PINGU sensitivities to DM self-interaction cross section σχχ are estimated for track and cascade events.

Highlights

We study the capture, annihilation and evaporation of dark matter (DM) inside the Sun
We demonstrate that this enhancement becomes more significant in the regime of small DM mass, given a fixed DM self-interaction cross section
In their work the evaporation effect can be neglected for the considered DM mass region and the detectability of σχχ by the IceCube through observing the final state neutrino flux produced by the DM annihilation is analyzed

Summary

DM evolution equation

We assume that both the galactic DM and the nuclei inside the Sun follow the thermal distributions. The inclusion of DM self-interaction will have effects on the capture and evaporation of DM inside the Sun. We will come to details of this in the later discussion. The capture rate from spin-independent (SI) scattering is given by [6, 7]. DM within the Sun, nχ is the local number density of halo DM, σχχ is the elastic scattering cross section of DM with themselves, vesc(R ) is the Sun’s escape velocity at the surface, and η2 = 3(v /v)2/2 is the square of a dimensionless velocity of the Sun through the Galactic halo with v = 220 km/s Sun’s velocity and v = 270 km/s the local velocity dispersion of DM in the halo. Is the DM effective volume inside the Sun and σv is the relative velocity averaged annihilation cross section.

Numerical results

Probing DM self-interaction at IceCube-PINGU

Conclusion

Findings

A DM self-interaction induced evaporation