Commissioning Run of the CRESST-II Dark Matter Search

TL;DR

The paper reports on the commissioning run of the upgraded CRESST-II experiment, demonstrating improved sensitivity in detecting potential WIMP dark matter interactions through cryogenic detectors with enhanced shielding and analysis techniques.

Contribution

It presents the first results from the CRESST-II upgrade, including detector performance, neutron test validation, and initial dark matter search limits with improved background suppression.

Findings

Approximately tenfold reduction in background events compared to previous results.

Detection of three tungsten recoil candidate events.

Set a WIMP-nucleon cross-section limit of 4.8 x 10^{-7} pb at 50 GeV mass.

Abstract

The CRESST cryogenic direct dark matter search at Gran Sasso, searching for WIMPs via nuclear recoil, has been upgraded to CRESST-II by several changes and improvements.We present the results of a commissioning run carried out in 2007. The basic element of CRESST-II is a detector module consisting of a large (~ 300 g) CaWO_4 crystal and a very sensitive smaller (~ 2 g) light detector to detect the scintillation light from the CaWO_4.Information from light-quenching factor studies allows the definition of a region of the energy-light yield plane which corresponds to tungsten recoils. A neutron test is reported which supports the principle of using the light yield to identify the recoiling nucleus. Data obtained with two detector modules for a total exposure of 48 kg-days are presented. Judging by the rate of events in the "all nuclear recoils" acceptance region the apparatus shows a factor ~ten improvement with respect to previous results, which we attribute principally to the presence of the neutron shield. In the "tungsten recoils" acceptance region three events are found, corresponding to a rate of 0.063 per kg-day. Standard assumptions on the dark matter flux, coherent or spin independent interactions,then yield a limit for WIMP-nucleon scattering of 4.8 \times 10^{-7}pb, at M{WIMP} ~50 GeV.