WIMP astronomy and particle physics with liquid-noble and cryogenic direct-detection experiments

Abstract

Once weakly-interacting massive particles (WIMPs) are unambiguously detected in directdetection experiments, the challenge will be to determine what one may infer from the data. Here, I examine the prospects for reconstructing the local speed distribution of WIMPs in addition to WIMP particle-physics properties (mass, cross sections) from next-generation cryogenic and liquidnoble direct-detection experiments. I find that the common method of fixing the form of the velocity distribution when estimating constraints on WIMP mass and cross sections means losing out on the information on the speed distribution contained in the data and may lead to biases in the inferred values of the particle-physics parameters. I show that using a more general, empirical form of the speed distribution can lead to good constraints on the speed distribution. Moreover, one can use Bayesian model selection criteria to determine if a theoretically-inspired functional form for the speed distribution (such as a Maxwell-Boltzmann distribution) fits better than an empirical model. The shape of the degeneracy between WIMP mass and cross sections and their offset from the true values of those parameters depends on the hypothesis for the speed distribution, which has significant implications for consistency checks between direct-detection and collider data. In addition, I find that the uncertainties on theoretical parameters depends sensitively on the upper end of the energy range used for WIMP searches. Better constraints on the WIMP particle-physics parameters and speed distribution are obtained if the WIMP search is extended to higher energy (∼ 1 MeV).

Galactic searches for dark matter

“…Because the SHM is probably only an approximation to the WIMP velocity distribution, and because a range of uncertain Galactic model parameters contribute to the determination of the WIMP event rate, when a detection is confirmed a more rigorous model for the Galactic dark matter distribution will be required. Using a discrete binned model for the WIMP velocity distribution, Peter (2011) and Kavanagh and Green (2012) still show that there is a significant degeneracy in the reconstruction of the WIMP mass and cross section. Combining data from different nuclear targets does improve the constraining power on these quantities.…”

Probing WIMP particle physics and astrophysics with direct detection and neutrino telescope data

“…Ref. [4]). Data analyses usually use the so-called standard halo model (SHM), where the velocity distribution is assumed to have the following simple form (in the Galactic rest frame):…”

Prospects for direct detection of dark matter in an effective theory approach

“…The prospects for direct detection of dark matter with ton-scale detectors have been analyzed using complementary approaches. Interesting investigations performed in this context include applications of the extended Likelihood approach [14], studies of the interplay of Bayesian and frequentists statistics [15,16], analyses of the complementarity of different detection strategies [17] and target materials [18][19][20], attempts to reconstruct the local dark matter velocity distribution [20][21][22][23], and an exploration of the Sun's gravitational focusing effect [24].…”