Measurement of nuclear recoil quenching factors in CaWO4

Abstract The CRESST experiment, aiming at the direct detection of WIMPs via nuclear recoils, is currently using scintillating CaWO 4 crystals. The WIMP–nucleus cross section for elastic scattering as well as the scintillation efficiency differ considerably for recoils from Ca, W and O in these crystals. Therefore a discriminating detector calibration is essential in order to improve WIMP parameter claims. At the tandem accelerator of the Maier-Leibnitz-Laboratory (MLL) in Garching, Germany, a neutron scattering facility is operated for the determination of the individual quenching factors (QF) in the bulk of a CaWO 4 crystal to better understand the detector response to neutron background and a possible WIMP signal. First measurements at room temperature reveal QF(O) = 7.8 ± 0.3% (recoil energy 1.0–2.2 MeV), QF(Ca) = 6.3 ± 1.6% (recoil energy 0.4–1 MeV), QF(W)  σ , recoil energy 0.1 MeV).