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) CaWO4 crystal and a very sensitive smaller (∼ 2 g) light detector to detect the scintillation light from the CaWO4. 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 lightquenching 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 × 10 −7 pb, at M WIMP ∼ 50 GeV.

Cornering light neutralino dark matter at the LHC

“…is an attractive possibility, because the parameter space selected by this scenario unavoidably corresponds to a large scattering cross-section with nuclei (up to σ SI 10 −41 cm 2 ), so that the signals at DAMA [12,13], CoGeNT [14], CRESST-II [15] and the three events recently reported by CDMS [16] could be nicely explained [7,17,18,19]. However, recent LHC results exclude light DM in this parameter region of the MSSM.…”

“…[20,21,22,19,23,36,52]), aiming at a possible explanation of the annual modulation signal at DAMA/LIBRA [12,13] and also reported by CoGeNT [14] and the excess of nuclear recoil events observed by CoGeNT itself and CRESST [15]. Recently, three signal events have been also reported by CDMS [16].…”

Unitarity and monojet bounds on models for DAMA, CoGeNT, and CRESST-II

“…There is therefore the possibility that a one-to-one correspondence can be established between MET rates at colliders and scattering rates at direct detection experiments. Indeed, the status of DM direct detection, with the three experiments DAMA [1], CoGeNT [2], and CRESST-II [3] reporting excesses consistent with a 10 GeV DM candidate, cries out for an independent, astrophysics-free verification. This has recently stimulated significant work aiming at a consistent explanation of these experiments [4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

Searching for dark matter subhalos in the Fermi-LAT second source catalog

“…This scenario is further supported by the peculiar spectral radio features observed from many of the Milky Way's non-thermal radio filaments [20] and by the Inner Galaxy's microwave haze [21], each of which can be explained by annihilating dark matter with the same mass, annihilations channels, cross section, and halo profile as are required to produce the gamma ray signal from the Galactic Center. Furthermore, a number of direct detection experiments (DAMA/LIBRA [22], CoGeNT [23] and CRESST-II [24]) have reported signals consistent with ∼10 GeV dark matter particles [25].…”