In-situ study of light production and transport in phonon/light detector modules for dark matter search

TL;DR

This study introduces a novel in-situ method for evaluating light production and transport in phonon/light detector modules used in dark matter searches, enabling more accurate characterization during actual experiments.

Contribution

The paper presents a new in-situ approach to assess light yield and transport efficiency in detector modules during dark matter search operations, unlike previous dedicated setup methods.

Findings

Approximately 20% of scintillation light is detected with current detectors.

Some light is absorbed creating meta-stable excitations in crystals.

Adding an extra light detector can increase detected light fraction.

Abstract

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.