In-situ study of light production and transport in phonon/light detector
  modules for dark matter search
  The CRESST experiment (Cryogenic Rare Event Search with Superconducting
Thermometers) searches for dark matter via the phonon and light signals of
elastic scattering processes in scintillating crystals. The discrimination
between a possible dark matter signal and background is based on the light
yield. We present a new method for evaluating the two characteristics of a
phonon/light detector module that determine how much of the deposited energy is
converted to scintillation light and how efficiently a module detects the
produced light. In contrast to former approaches with dedicated setups, we
developed a method which allows us to use data taken with the cryogenic setup,
during a dark matter search phase. In this way, we accounted for the entire
process that occurs in a detector module, and obtained information on the light
emission of the crystal as well as information on the performance of the module
(light transport and detection). We found that with the detectors operated in
CRESST-II phase 1, about 20% of the produced scintillation light is detected. A
part of the light is likely absorbed by creating meta-stable excitations in the
scintillating crystals. The light not detected is not absorbed entirely, as an
additional light detector can help to increase the fraction of detected light.
