B. Majorovits

Limits on WIMP dark matter using scintillating CaWO4 cryogenic detectors with active background suppression

We present first significant limits on WIMP dark matter by the phonon-light technique, where combined phonon and light signals from a scintillating cryogenic detector are used. Data from early 2004 with two 300xa0g CRESST-II prototype detector modules are presented, with a net exposure of 20.5xa0kg days. The modules consist of a CaWO4 scintillating “target” crystal and a smaller cryogenic light detector. The combination of phonon and light signals leads to a strong suppression of non-nuclear recoil backgrounds. Using this information to define an acceptance region for nuclear recoils we have 16 events from the two modules, corresponding to a rate for nuclear recoils between 12 and 40xa0keV of (0.87xa0±xa00.22) events/(kgxa0day). This is compatible with the rate expected from neutron background, and most of these events lie in the region of the phonon-light plane anticipated for neutron-induced recoils. A particularly strong limit for WIMPs with coherent scattering results from selecting a region of the phonon-light plane corresponding to tungsten recoils, where the best module shows zero events.

Commissioning run of the CRESST-II dark matter search

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. The upgrade includes a new detector support structure capable of accommodating 33 modules, the associated multichannel readout with 66 SQUID channels, a neutron shield, a calibration source lift, and the installation of a muon veto. 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 . The large crystal gives an accurate total energy measurement. The light detector permits a determination of the light yield for an event, allowing an effective separation of nuclear recoils from electron–photon backgrounds. Furthermore, 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 48xa0kg-days are presented. Judging by the rate of events in the “all nuclear recoils” acceptance region the apparatus shows a factor ∼10 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 0.063xa0per 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 × 10 - 7 pb , at M WIMP ∼ 50 GeV .

Detection of the natural {alpha} decay of tungsten

The natural

Detection of the naturalαdecay of tungsten

ensuremath{alpha}

Electron and gamma background in CRESST detectors

-decay of

The 66-channel SQUID readout for CRESST II

^{180}mathrm{W}

Production of low-background CuSn6-bronze for the CRESST dark-matter-search experiment

has been unambiguously detected for the first time. The

Development of superconducting contacts for the CRESST II 66-channel superconducting quantum interference device readout system

ensuremath{alpha}

THE CRESST DARK MATTER SEARCH

peak is found in a (

Results and status of the CRESST experiment

ensuremath{gamma}