The CRESST dark matter search

Abstract

Abstract. We present the current status of CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) project and new results concerning detector development. The basic technique involved is to search for WIMPs by the measurement of non-thermal phonons, as created by WIMP-induced nuclear recoils. Combined with our newly developed method for the simultaneous measurement of scintillation light, strong background discrimination is possible, resulting in a substantial increase in WIMP detection sensitivity. CRESST and the Dark Matter ProblemAfter a long period of development, cryogenic detectors are now coming on line and deliver significant results in particle-astrophysics and weak interactions. The goal of the CRESST project is the direct detection of elementary particle dark matter and the elucidation of its nature. Particle physics provides a well motivated dark matter candidate through the lightest supersymmetric (SUSY) particle, the 'neutralino' and one can find candidates in a wide mass range [1]. Generically, such particles are called WIMPS (Weakly Interacting Massive Particles). WIMPS are expected to interact with ordinary matter by elastic scattering on nuclei. Conventional methods for direct detection rely on the ionization or scintillation caused by the recoiling nucleus. This leads to limitations connected with the relatively high energy involved in producing electron-hole pairs. Cryogenic detectors use the much lower energy excitations, such as phonons. Since the principal physical effect of a WIMP nuclear recoil is the generation of phonons, cryogenic calorimeters are well suited for WIMP detection. Further, when this technology is combined with charge or light detection the resulting background suppression leads to a powerful technique to search for the rare nuclear recoils.The detectors developed by the CRESST collaboration consist of a dielectric target-crystal with a small superconducting film evaporated onto the surface. When this film is held at a temperature in the middle of its superconducting to normal conducting phase transition, it functions as a highly sensitive thermometer. The detectors presently employed in Gran Sasso use tungsten (W) films and sapphire (Al 2 O 3 ) absorbers, running near 15 mK. The technique can 2 J. Jochum CRESST collabroation also be applied to a variety of other materials. The small change in temperature of the superconducting film resulting from an energy deposit in the target leads to a relatively large change in the film's resistance. This change in resistance is measured with a SQUID. A small separate detector of the same type is used to see the light emitted when the target is a scintillating crystal. Present Status of CRESSTThe task set for the first stage of CRESST was to show the operation of four 262 g sapphire detectors, with a threshold of 500 eV under low background conditions. Meeting this goal involved the setting up of a low background, large volume, cryogenic installation and the development of massive, low background detectors with low ...

Mixed higgsino dark matter from a large SU(2) gaugino mass

“…Although there is no positive signal to date, the most stringent upper limit on the scattering crosssection comes from the XENON-10 collaboration [47], which obtained an upper limit σ( Z 1 p) < ∼ 8 × 10 −8 pb for m e Z 1 ∼ 100 GeV, corresponding to the expected neutralino mass in the HM2DM model for our canonical choice of parameters in figure 1. We compute the spin independent neutralino-proton scattering cross-section (used as the figure of merit in these experiments), and compare it to projections for the sensitivity of Stage 2 detectors (CDMS2 [48], Edelweiss2 [49], CRESST2 [50], ZEPLIN2 [51]) which are expected to probe a factor of ∼ 5 below the XENON-10 bound. 7 We also compare expectations in the HM2DM model with the projected sensitivity of the proposed SuperCDMS detector with 25 kg of Ge, and with proposed ton-size noble liquid detectors (XENON [53], LUX, WARP [54] and CLEAN [55]), for which we use the sensitivity of Warm Argon Project, with 1400 kg of argon as the benchmark.…”

“…[78]. In addition to the various geometric and other acceptance requirements, we required the following analysis cuts on the signal: 150,150,80,50) GeV,…”

Prospects for detecting supersymmetric dark matter at Post-LEP benchmark points

“…Fig. 2 shows the projected sensitivities (a,b) for CDMS II [35] and CRESST [36] (solid) and GENIUS [37] (dashed), and (c) a 100 kg NAIAD [38] detector, as well as (d) the existing DAMA limit [39]. Obtaining a competitive limit for the spin-dependent scattering on a neutron in the latter case might be possible with a large 73 Ge or Xenon detector.…”

The enigma of the dark matter

“…Apart from the two already discussed DAMA and HDMS, there are three other experiments in prospect, CRESST, CUORE and GENIUS. For example, the Cryogenic Rare Event Search using Superconducting Thermometers (CRESST) experiment [18], which involves the Max Planck Institute for Physics, the Technical University in Munich, the Gran Sasso, and the University of Oxford, measures simultaneously phonons and scintillation light distinguishing the nuclear recoils from the electron recoils cause by background radioactivity. In contrast to other experiments, CRESST detectors allow the employment of a large variety of target materials, such as e.g.…”