CsI(Tl) for WIMP dark matter searches

TL;DR

This study evaluates CsI(Tl) scintillators for dark matter detection, demonstrating improved recoil discrimination and sensitivity over NaI(Tl), especially for spin-independent WIMP interactions, based on pulse shape analysis and quenching factor measurements.

Contribution

The paper provides the first detailed assessment of CsI(Tl) for WIMP searches, highlighting its superior discrimination and sensitivity compared to NaI(Tl).

Findings

Pulse shape analysis discriminates electron and nuclear recoils down to 4 keV.

Discrimination factor is 10-15% better than NaI(Tl) above 4 keV.

Potential sensitivity to WIMPs is up to five times higher than NaI(Tl).

Abstract

We report a study of CsI(Tl) scintillator to assess its applicability in experiments to search for dark matter particles. Measurements of the mean scintillation pulse shapes due to nuclear and electron recoils have been performed. We find that, as with NaI(Tl), pulse shape analysis can be used to discriminate between electron and nuclear recoils down to 4 keV. However, the discrimination factor is typically (10-15)% better than in NaI(Tl) above 4 keV. The quenching factor for caesium and iodine recoils was measured and found to increase from 11% to ~17% with decreasing recoil energy from 60 to 12 keV. Based on these results, the potential sensitivity of CsI(Tl) to dark matter particles in the form of neutralinos was calculated. We find an improvement over NaI(Tl) for the spin independent WIMP-nucleon interactions up to a factor of 5 assuming comparable electron background levels in the two scintillators.