Modulation effect for supersymmetric dark matter detection with asymmetric velocity dispersion

Abstract

The detection of the theoretically expected dark matter is central to particle physics cosmology. Current fashionable supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). Such models conmbined with fairly well understood physics like the quark substructure of the nucleon and the nuclear form factor and/or the spin response function of the nucleus, permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates are, however, very low or even undetectable. So it is imperative to exploit the modulation effect, i.e. the dependence of the event irate on the earth's annual motion. In this paper we study such a modulation effect both in non directional and directional experiments. We calculate both the differential and the total rates using symmetric as well as asymmetric velocity distributions. We find that in the symmetric case the modulation amplitude is small, less than 0.07. There exist, however, regions of the phase space and experimental conditions such that the effect can become larger. The inclusion of asymmetry, with a realistic enhanced velocity dispersion in the galactocentric direction, yields the bonus of an enhanced modulation effect, with an amplitude which for certain parameters can become as large as 0.46

Dependence of direct detection signals on the WIMP velocity distribution

“…It is well known, however, that the energy [17,18,75,36,37,32,34,35,40,41], time [19,20,21,22,23,24,25,26,36,37,38,32,34,35,40] and direction [27,28,29,34] dependence of the direct detection event rate all depend on the local WIMP distribution. We have updated these studies in light of recent numerical simulations and observational measurements of the local circular speed and escape speed.…”

“…The energy [17,18], time [19,20,21,22,23,24,25,26] and direction [27,28,29] dependence of the event rate all depend on the ultra-local WIMP distribution. Historically analytic halo models have been used to calculate the WIMP signals and analyse data.…”

The soft supersymmetry-breaking Lagrangian: theory and applications

“…The recoil energy Q r is typically no more than 100 keV. The greatest uncertainty in the differential detection rate is from the uncertainty in the local LSP density ρ χ [481,482,483,484,485,486,487,488,489,490,491,492,493]; the answer is uncertain by a factor of a few. When folded in with the nuclear physics uncertainties, the final theoretical detection rate is uncertain by about a factor of 10 or more.…”

Searching for supersymmetric dark matter: The directional rate and the modulation effect due to caustic rings

“…The difference between the maximum and the minimum is about 4%, a bit smaller than that predicted by the symmetric isothermal models. It is, however, substantially less than h = 0.46 predicted by asymmetric isothermal velocity distribution 16,17 .…”

“…the modulation effect. In the past this has been accomplished by assuming a consistent LSP velocity dispersion, such as a Maxwell distribution 2 or asymmetric velocity distribution with enhanced dispersion in the galactocentric direction 31,16,17 . More recently other very interesting non-isothermal approaches have been proposed, which consider the in-fall of dark matter into the galaxy producing flows of caustic rings.…”