Abstract
Direct detection experiments tend to lose sensitivity in searches for sub-MeV light dark matter candidates due to the threshold of recoil energy. However, such light dark matter particles could be accelerated by energetic cosmic rays, such that they could be detected with existing detectors. We derive constraints on the scattering of a boosted light dark matter particle and electron from the XENON100/1T experiment. We illustrate that the energy dependence of the cross section plays a crucial role in improving both the detection sensitivity and also the complementarity of direct detection and other experiments.
Highlights
Direct detection experiments turn to lose sensitivity of searching for a sub-MeV light dark matter candidate due to the threshold of recoil energy
Light dark matter (DM) candidate is well motivated and can be naturally realized when the DM candidate couples feebly to visible sector [1,2,3,4,5]. It is difficult for a sub-MeV DM candidate to satisfy observed relic abundance through the thermal freeze-out mechanism [6,7,8]; freeze-in via annihilation of electron-positron pairs is a primary mechanism for DM production [2, 3, 9]
The traditional direct detection of DM-nucleus scattering loses sensitivity rapidly for a DM candidate whose mass is below ∼ GeV due to the threshold of recoil energy
Summary
Where mχ and mA denote the mass of DM candidate and the dark photon, respectively. gχ and gSM are the coupling strength of A to the DM candidate and the electron, respectively. Where mχ and mA denote the mass of DM candidate and the dark photon, respectively. Gχ and gSM are the coupling strength of A to the DM candidate and the electron, respectively. When the DM candidate scatters off an incident CR electron with a given kinetic energy (TCR), the distribution of the DM recoil energy Tχ is dσχe dTχ. Where σe denotes the cross section of DM-free electron scattering for a fixed momentum transfer q = αme [3]. The maximal recoil energy of the DM candidate is [23]. Convoluting the Tχ distribution in Eq (2) with the energy spectrum of incident CR electrons dΦe/dTCR yields the recoil flux of boosted DM candidate [20]
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