Abstract
We study novel scenarios where thermal dark matter (DM) can be efficiently captured in the Sun and annihilate into boosted dark matter. In models with semi-annihilating DM, where DM has a non-minimal stabilization symmetry, or in models with a multi-component DM sector, annihilations of DM can give rise to stable dark sector particles with moderate Lorentz boosts. We investigate both of these possibilities, presenting concrete models as proofs of concept. Both scenarios can yield viable thermal relic DM with masses O(1)-O(100) GeV. Taking advantage of the energetic proton recoils that arise when the boosted DM scatters off matter, we propose a detection strategy which uses large volume terrestrial detectors, such as those designed to detect neutrinos or proton decays. In particular, we propose a search for proton tracks pointing towards the Sun. We focus on signals at Cherenkov-radiation-based detectors such as Super-Kamiokande (SK) and its upgrade Hyper-Kamiokande (HK). We find that with spin-dependent scattering as the dominant DM-nucleus interaction at low energies, boosted DM can leave detectable signals at SK or HK, with sensitivity comparable to DM direct detection experiments while being consistent with current constraints. Our study provides a new search path for DM sectors with non-minimal structure.
Highlights
We focus on two concrete scenarios: models with semi-annihilation of one dark matter (DM) species ψ charged under a Z3 symmetry, and models with a two-component DM sector with species ψA and ψB having masses mA > mB and ψA being the dominant DM component
We focus only on the simplest version of semi-annihilation model where we assume a single DM particle χ charged under a Z3 symmetry, which protects χ from decay
We investigate a new search channel for boosted DM
Summary
The evidence for the existence of particulate Dark Matter (DM) [1,2,3] is extremely compelling. If interactions with electrons are suppressed or if the mediator is heavier than O(10 MeV), the detection via interactions with quarks is important These interactions can enhance the flux of boosted DM by generating a large rate of DM capture and subsequent annihilation in the Sun. For a broad range of parameters, the flux from the Sun will dominate over the flux from the galactic center, making it possible to have observable signals with scattering cross sections of weak scale size or even smaller. Annihilation into dark sector particles, as occurs in both our two-component DM or semiannihilating DM examples, evades strong constraints from DM detection experiments in a natural way, while still allowing for a thermal freeze-out origin of DM This is complementary to other variations such as models where DM annihilates into dark radiation or to dark states that decay back to the SM, as discussed in Ref.
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