Is the effect of the Sun's gravitational potential on dark matter particles observable?

Abstract

We consider the effect of the Sun's gravitational potential on the local phase space distribution of dark matter particles, focusing on its implication for the annual modulation signal in direct detection experiments. We perform a fit to the modulation signal observed in DAMA/LIBRA and show that the allowed region shrinks if Solar gravitational focusing (GF) is included compared to the one without GF. Furthermore, we consider a possible signal in a generic future direct detection experiment, irrespective of the DAMA/LIBRA signal. Even for scattering cross sections close to the current bound and a large exposure of a xenon target with 270 ton yr it will be hard to establish the presence of GF from data. In the region of dark matter masses below 40 GeV an annual modulation signal can be established for our assumed experimental setup, however GF is negligible for low masses. In the high mass region, where GF is more important, the significance of annual modulation itself is very low. We obtain similar results for lighter targets such as Ge and Ar. We comment also on inelastic scattering, noting that GF becomes somewhat more important for exothermic scattering compared to the elastic case.

19 pages, 20 figures, 1 table, v2: added Fig. 3 for DAMA, and comments on light targets

References in corpus (7)

• Dark Matter Results from 225 Live Days of XENON100 Data
• New results from DAMA/LIBRA
• Exciting Dark Matter and the INTEGRAL/SPI 511 keV signal
• Direct Detection of Multi-component Secluded WIMPs
• Exothermic Dark Matter
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Cited by in corpus (5)

• On the direct detection of multi-component dark matter: sensitivity studies and parameter estimation
• Directional detection of dark matter streams
• Dark Matter vs. Neutrinos: The effect of astrophysical uncertainties and timing information on the neutrino floor
• Gravitational focusing effects on streaming dark matter as a new detection concept
• A halo-independent lower bound on the dark matter capture rate in the Sun from a direct detection signal