Abstract
It has been found that a pseudo-Nambu-Goldstone boson dark matter suppresses the amplitude for elastic scattering with nuclei in non-relativistic limit, and thus can naturally evade the strong constraint of dark matter direct detection experiments. In this paper, we show that non-zero elastic scattering cross section can be induced if the mediator mass is as small as momentum transfer. The predicted recoil energy spectrum can differ from that for usual thermal dark matter. Together with the relevant constraints such as thermal relic abundance, indirect detection and Higgs decays, we investigate the detectability through the current and future dark matter direct detection experiments.
Highlights
Dark matter direct detection experiments impose strong bounds on thermal dark matter
This is because the amplitude of the elastic scattering with nuclei is suppressed by the small momentum of dark matter through the derivative coupling
We have focused on the case that the particle mediating the elastic scattering is light enough, and we have found that a nonzero contribution to the amplitude emerges
Summary
Dark matter direct detection experiments impose strong bounds on thermal dark matter. The pseudo-Nambu-Goldstone boson (pNGB) dark matter has been proposed as a candidate naturally evading this strong constraint [4] This is because the amplitude of the elastic scattering with nuclei is suppressed by the small momentum of dark matter through the derivative coupling. It may be natural that the scale of the soft breaking term is much smaller than the scale of the spontaneous symmetry breaking in the sense that the global symmetry is approximate This is not necessarily true if a ultra-violet (UV) completion of the pNGB model is considered [9,10,11,12]. We consider the pNGB dark matter with a light mediator In this scenario, we will show that non-zero elastic scattering cross section between dark matter and nuclei emerges even though the interactions arise from the derivative coupling. We show that some parameter region has already been excluded by the XENON1T bound, and some other region will be explored by the future XENONnT experiment
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