CsI(Tl) for WIMP dark matter searches

We report a study of CsI(T1) scintillator to assess its applicability in ex periments to search for dark matter particles. Measurements of the mean sci ntillation pulse shapes due to nuclear and electron recoils have been perfo rmed. We find that, as with NaI(T1). pulse shape analysis can be used to di scriminate between electron and nuclear recoils down to 4 keV. However, the discrimination factor is typically 10-15% better than in NaI(T1) above 4 k eV. The quenching factor for caesium and iodine recoils was measured and fo und to increase from 11% to similar to 17% with decreasing recoil energy fr om 60 to 12 keV. Based on these results, the potential sensitivity of CsI(T 1) to dark matter particles in the form of neutralinos was calculated. We f ind an improvement over NaI(T1) for the spin-independent WIMP-nucleon inter actions up to a factor of 5 assuming comparable electron background levels in the two scintillators. (C) 2001 Elsevier Science B.V. All rights reserve d.