Abstract
We study the impact of the assumed velocity distribution of galactic dark matter particles on the interpretation of results from nuclear recoil detectors. By converting experimental data to variables that make the astrophysical unknowns explicit, different experiments can be compared without implicit assumptions concerning the dark matter halo. We extend this framework to include the annual modulation signal, as well as multiple target elements. Recent results from DAMA, CoGeNT and CRESST-II can be brought into agreement if the velocity distribution is very anisotropic and thus allows a large modulation fraction. However constraints from CDMS and XENON cannot be evaded by appealing to such astrophysical uncertainties alone.
Highlights
We study the impact of the assumed velocity distribution of galactic dark matter particles on the interpretation of results from nuclear recoil detectors
We use the events reported by CoGeNT and CRESST-II to measure g(vmin) and the null results from XENON, CDMS, SIMPLE and the CRESST-II commissioning run to constrain it
As we increase mχ the exclusion curves as well as the CoGeNT data points move according to vmin ∼ 1/mχ — the CRESST-II data points and exclusion curves scale differently because the mass of oxygen is comparable to mχ in the lower panels
Summary
We study the impact of the assumed velocity distribution of galactic dark matter particles on the interpretation of results from nuclear recoil detectors. Results from direct detection experiments are usually presented as a signal or exclusion curve in the parameter plane of DM mass versus its scattering cross-section, assuming a Maxwell-Boltzmann (M-B) velocity distribution with a cut-off at the escape velocity from the Galaxy. This is known as the Standard Halo Model (SHM). Rather than probing the velocity distribution, direct detection experiments measure the velocity integral: g(vmin) = vmin f (v)/v d3v It was suggested [12] that results from one experiment be converted into vminspace in order to predict the event rate in a second experiment, without having to make any assumptions concerning the astrophysics. Our approach is complementary to the usual analysis of direct detection experiments, wherein the astrophysical parameters are held fixed and the DM mass and cross-section are allowed to vary
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