Abstract
We show that current and imminent underground detectors are capable of precision astrometry of dark matter. First we show that galactic dark matter velocity distributions can be obtained from reconstructed tracks of dark matter scattering on multiple nuclei during transit; using the liquid scintillator neutrino detector SNO+ as an example, we find that the dark matter velocity vector can be reconstructed event-by-event with such a small uncertainty, that the precision of dark matter astrometry will be limited mainly by statistics. We then determine the number of dark matter events required to determine the dispersion speed, escape speed, and velocity anisotropies of the local dark matter halo, and also find that with as few as $\mathcal{O}(10)$ events, dark matter signals may be discriminated from potential backgrounds arising as power-law distributions. Finally, we discuss the prospects of dark matter astrometry at other liquid scintillator detectors, dark matter experiments, and the recently proposed MATHUSLA detector.
Highlights
While the search for particle dark matter colliding at most once per transit through underground detectors has proceeded apace, the study of dark matter scattering multiple times has recently received reinvigorated research.It has been shown that dark matter candidates expected to interact multiple times in detectors can be discovered using entirely new analyses at both traditional single-scatter dark matter experiments and neutrino detectors [1,2]
SNOþ would in the near future search for neutrinoless double beta decay of tellurium (130Te) loaded into the liquid scintillator linear alkyl benzene (LAB)
As discussed in Ref. [2], for multiscattering dark matter to be discovered at this experiment, we conservatively require a minimum of approximately 100 photons produced and detected by photomultiplier tube (PMT) during the approximately 10 μs transit of a multiscattering particle
Summary
While the search for particle dark matter colliding at most once per transit through underground detectors has proceeded apace, the study of dark matter scattering multiple times has recently received reinvigorated research. Our strategy will be to reconstruct the track of a dark matter particle traversing the inner detector, utilizing the fact that the heavy dark matter particle essentially transits the detector in a straight line at constant speed, with scintillation light originating from the points along this track where much lighter nuclei recoil This strategy is similar to previous efforts involving leptons produced by charged current events, there are two key distinctions: (1) the dark matter tracks we construct will generate fewer PMT hits, and (2) these hits will be more widely spaced in time since dark matter moves more slowly.
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