The CRESST Dark Matter Search

Abstract

The CRESST cryogenic direct Dark Matter search is located in the Gran Sasso underground laboratories. CaWO4 crystals have been used as scintillating targets for WIMP interactions. Each crystal is operated as a cryogenic calorimeter in combination with a second cryogenic detector used to measure the scintillation light produced in the target crystal. For each particle interaction, the combination of phonon and light signals enables an event by event discrimination allowing an effective separation of nuclear recoils from electron-photon backgrounds. Furthermore, information from studies on the light yield of different nuclear recoils allows the definition of a region of the energy-light yield plane which corresponds to tungsten recoils. After a major upgrade of the setup which includes a new detector support structure capable of accommodating 33 detector modules, the associated multichannel readout with 66 SQUID channels, a neutron shield, a calibration source lift and the installation of a muon veto, the experiment has been successfully commissioned and data from the commissioning phase carried out in 2007 collected with two detector modules (total exposure of  48 kg-days) are presented here. With standard assumptions on the dark matter flux, the three events found in the “tungsten recoils” acceptance region yield a limit of 4:810_s13_s171048576_s197 pb at MWIMP  50 GeV for coherent or spin-independent WIMP-nucleon scattering cross section.