Dark matter in the Sun: scattering off electrons vs nucleons

Abstract

The annihilation of dark matter (DM) particles accumulated in the Sun could produce a flux of neutrinos, which is potentially detectable with neutrino detectors/telescopes and the DM elastic scattering cross section can be constrained. Although the process of DM capture in astrophysical objects like the Sun is commonly assumed to be due to interactions only with nucleons, there are scenarios in which tree-level DM couplings to quarks are absent, and even if loop-induced interactions with nucleons are allowed, scatterings off electrons could be the dominant capture mechanism. We consider this possibility and study in detail all the ingredients necessary to compute the neutrino production rates from DM annihilations in the Sun (capture, annihilation and evaporation rates) for velocity-independent and isotropic, velocity-dependent and isotropic and momentum-dependent scattering cross sections for DM interactions with electrons and compare them with the results obtained for the case of interactions with nucleons. Moreover, we improve the usual calculations in a number of ways and provide analytical expressions in three appendices. Interestingly, we find that the evaporation mass in the case of interactions with electrons could be below the GeV range, depending on the high-velocity tail of the DM distribution in the Sun, which would open a new mass window for searching for this type of scenarios.

Constraints on dark matter from the Moon

“…Before we proceed to estimate the evaporation and annihilation rates we have to determine the distribution of DM particles in the Moon once they are thermalized. To this end we compute the DM distribution semianalytically using methods described in [4,5,33]. For σ n < 10 −33 cm 2 , i.e.…”

The distribution of inelastic dark matter in the Sun

“…(30), keeping the above caveat at the back of the mind. When the mean free path of DM inside the Sun is much larger than the solar radius (as considered here), the radial number density distribution is often approximated as an isothermal Maxwell-Boltzmann distribution that can be written as [12,17,28,59,66,67] …”

Dark matter capture by the Sun: revisiting velocity distribution uncertainties

“…The description and formalism of WIMP capture by the Sun can be found in e.g [1,14,32,[51][52][53]. The change in the number, N , of captured WIMPs inside the Sun is described by the competition between the rate of capture, C, and two times the annihilation rate of the already captured WIMPs in the centre of the Sun, Γ A = 1 2 C A N 2 (as long as the DM mass m χ > 5 GeV where WIMP evaporation is not relevant [14,32,51,54]). Once the age of the Sun is greater than the time needed for the capture and annihilation processes to equilibrate, τ = (CC A ) −1/2 , the annihilation rate becomes proportional to one half of the capture rate.…”

“…Even if indirect detection with neutrino telescopes have failed to identify a signal, tight limits have been imposed on DM-nucleon interaction cross-section by different neutrino detectors [27][28][29][30][31]. The formalism and uncertainties related to DM capture by the Sun are treated in [1,32], we revisit in this work the astrophysical uncertainties related to dark matter distributions such as the local DM density and velocity distribution. Different assumptions can be inferred from cosmological simulations, galactic dynamics and other approaches (see e.g [33][34][35][36][37][38]).…”