Constraints on leptophilic light dark matter from internal heat flux of Earth

Dark matter (DM) in Earth-intersecting orbits can scatter off electrons and lose energy, and be gravitationally bound to the Earth. Eventually, they lose enough energy and accumulate at the core. It is assumed that DM annihilates/decays predominantly into Standard Model particles inside the Earth. The heat flux from these processes is compared with the experimentally measured value of the internal heat flux of the Earth, which is 44 TW. Assuming a steady state between capture and annihilation/decay, we put constraints on the scattering cross section of DM with electrons as a function of their mass. For low-mass regions (<10-2 GeV), these constraints on leptophilic DM are better than those obtained from direct-detection experiments.