Abstract
Above a critical dark matter-nucleus scattering cross section any terrestrial direct detection experiment loses sensitivity to dark matter, since the Earth crust, atmosphere, and potential shielding layers start to block off the dark matter particles. This critical cross section is commonly determined by describing the average energy loss of the dark matter particles analytically. However, this treatment overestimates the stopping power of the Earth crust. Therefore the obtained bounds should be considered as conservative. We perform Monte Carlo simulations to determine the precise value of the critical cross section for various direct detection experiments and compare them to other dark matter constraints in the low mass regime. In this region we find parameter space where typical underground and surface detectors are completely blind to dark matter. This "hole" in the parameter space can hardly be closed with an increase in the detector exposure. Dedicated surface or high-altitude experiments may be the only way to directly probe this part of the parameter space.
Highlights
The existence of large quantities of dark matter (DM) in the universe is backed by strong astrophysical evidence [1,2]
We use Monte Carlo (MC) techniques to precisely determine this upper critical cross section, above which each experiment fails to probe DM. Previous works on this matter treated the stopping of DM in an overburden with analytic formulas which capture the average energy loss of DM particles traversing through the Earth crust [25,30,31,32,33]
We determine the precise critical DM-nucleon scattering cross section with MC techniques above which a given detector with a certain depth becomes blind to DM
Summary
The existence of large quantities of dark matter (DM) in the universe is backed by strong astrophysical evidence [1,2]. We use Monte Carlo (MC) techniques to precisely determine this upper critical cross section, above which each experiment fails to probe DM Previous works on this matter treated the stopping of DM in an overburden with analytic formulas which capture the average energy loss of DM particles traversing through the Earth crust [25,30,31,32,33]. Since the analytic description overestimates the stopping power of the Earth crust by capturing the average energy loss, the bounds obtained this way turn out to be conservative, and may be extended towards higher cross sections For this purpose dedicated MC simulations of DM particles propagating and scattering in the shielding layers are necessary, as first applied in this context in [26], to DM-electron scattering experiments in [34], and further developed, motivated and applied in [29,35]. The code DAMASCUS-CRUST developed for this paper is publicly available [42]
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