G. Gerbier et al., Pulse shape discrimination and dark matter search with NaI (Tl) scintillator at Laboratoire Souterrain de Modane, NUCL PH B-P, 87, 2000, pp. 61-63
Underground data for WIMP search have been obtained from a 83 days run in a
low activity environment at the Laboratoire Souterrain de Modane (LSM), wi
th a 10 kg NaI(Tl) detector. The obtained high photoelectron yield allowed
an energy threshold of 2 keV. A low energy peak in the energy spectrum limi
ts the sensitivity to Spin Independent coupling WIMP investigation. Pulse s
hape analysis of the data have shown an unexpected population of events, al
so observed by another experiment at the same rate. A possible interpretati
on of these events is related to alpha decays of radon isotope at the surfa
ce of the crystal.