Thermal transport of the solar captured dark matter and its impact on the indirect dark matter search

Abstract

We study the thermal transport occurring in the system of solar captured dark matter (DM) and explore its impact on the DM indirect search signal. We particularly focus on the scenario of self-interacting DM (SIDM). The flows of energies in and out of the system are caused by solar captures via DM-nucleon and DM-DM scatterings, the energy dissipation via DM annihilation, and the heat exchange between DM and solar nuclei. We examine the DM temperature evolution and demonstrate that the DM temperature can be higher than the core temperature of the Sun if the DM-nucleon cross section is sufficiently small such that the energy flow due to DM self-interaction becomes relatively important. We argue that the correct DM temperature should be used for accurately predicting the DM annihilation rate, which is relevant to the DM indirect detection. PACS numbers:Dark matter (DM) composes about 25% of the energy density of in the universe and plays an important role in the structure formation. It was shown that if the galactic halo is constituted by weakly interacting massive particles (WIMPs), there is a high possibility that these WIMPs are captured by the Sun [1-8, 10]. In general there are thermal energy flows between the captured DMs and the nuclei in the Sun. Microscopically, such flows are caused by particle scatterings. For collisionless cold dark matter (CCDM), the scatterings are only between the DM and solar nuclei. Regarding the huge difference in abundance between the two, it is reasonable to take the DM temperature to be identical to the core temperature of the Sun. However, the scenario of SIDM can change the picture dramatically. In such a scenario, the energy transports via DM self-capture and DM-nucleus scattering compete with each other. In particular, if DM-nucleus interaction is much weaker than expected, the thermal exchange between DMs and nuclei would be much less efficient. As a result, the DM temperature can be distinct from the solar core temperature.It is worth mentioning that the DM abundance is not much affected with a suppressed DM-nucleon cross section σ χp provided SIDM is considered [11]. The accumulated DM abundance is determined by the balance among the capture, the evaporation, and the annihilation rates. Earlier works on such processes only consider DM-nucleon interactions. The new effects from DM selfinteraction are investigated recently [8][9][10][11]. The consideration of SIDM comes from the discrepancies between the numerical N-body simulations using the hypothesis of CCDM and the astrophysical observations on the * small structure of the universe [12]. The CCDM simulations [13] predict cuspy profiles in the center regions of galaxies, which conflict with flatten cores found in our Milky Way (MW) [14], other nearby dwarfs [15], and low luminous galaxies [16,17]. There are additional puzzles concerning the sizes of subhalos. The observed MW satellites are hosted by much less massive subhalos compared to sizes of the most massive subhalos arising from simulations. The absence of such mas...

A solar system test of self-interacting dark matter

“…Adding dark matter self-interactions changes the above discussion in two ways. First and most importantly, self-interactions provide additional mechanisms for energy transfer into, among, and out of the captured DM population [64]. As our aim here is to establish the region where our ansatz describing the captured DM population as thermalized at the core temperature of the capturing body is self-consistent, the most important of these processes for our purposes is the net rate of energy injected into the captured dark matter population from scattering off of DM particles in the halo.…”

The distribution of inelastic dark matter in the Sun

“…The accumulation of large amounts of DM in the Sun may also affect helioseismology and the solar temperature. These modifications can potentially lead to observational effects with the possibility to constrain DM properties or alleviate the solar composition problem [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Analysis on the black hole formations inside old neutron stars by isospin-violating dark matter with self-interaction

“…The case for the solar-capture DM has been studied recently in refs. [15][16][17][18][19][20][21][22][23][24]. On the other hand, if captures happen in the compact stars such as neutron stars (NS), the annihilation products could potentially cause the surface temperature of the star deviating from the standard prediction .…”