Theoretical Interpretation of Experimental Data from Direct Dark Matter Detection

Abstract

Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. Currently, the most promising method to detect many difeerent WIMP candidates is the direct detection of the recoil energy deposited in a low-background laboratory detector due to elastic WIMP-nucleus scattering. So far the usual procedure has been to predict the event rate of direct detection of WIMPs based on some model(s) of the Galactic halo from cosmology and of WIMPs from elementary particle physics.<br /> The aim of this work is to invert this process. In this thesis I will present methods which allow to extract information on the WIMP velocity distribution function as well as on the WIMP mass from the recoil energy spectrum as well as from experimental data directly.<br /> At first I will derive the expression that allow to reconstruct the normalized one- dimensional velocity distribution function of WIMPs from the recoil spectrum. I will also derive the formulae for determining the moments of the velocity distribution function. All these expressions are independent of the as yet unknown WIMP density near the Earth as well as of the WIMP-nucleus cross section. The only information about the nature of WIMPs which one needs is the WIMP mass.<br /> Then I will present methods that allow to apply the expressions directly to exper- imental data, without the need to fit the recoil spectrum to a functional form. These methods are independent of the Galactic halo model. The reconstruction of the velocity distribution function will be further extended to take into account the annual modulation of the event rate.<br /> Moreover, I will present a method for reconstructing the amplitude of the annual mod- ulation of the velocity distribution. The only information which one needs is the measured recoil energies and their measuring times. An alternative, better way for confirming the annual modulation of the event rate will also be given.<br /> Finally, I will present a method for determining the WIMP mass by combining two (or more) experiments with difeerent detector materials. This method is not only independent of the model of Galactic halo but also of that of WIMPs. In addition, some meaningful information on the WIMP mass can already be extracted from less than one hundred events.