Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

Abstract

The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3 to 52 keV nr , covering the whole DAMA/LIBRA energy region for dark matter-Na scattering interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

Response of CsI[Na] to nuclear recoils: Impact on coherent elastic neutrino-nucleus scattering

“…This calibration setup was utilized in [6] to observe a monotonically decreasing QF with decreasing Na recoil energy in NaI[Tl], a trend at the time in tension with previous measurements. This behavior was later confirmed in four independent experiments [10][11][12][13].…”

Annual modulation in direct dark matter searches

“…As impurities concentrate in the growing tip of the crystal this last part can be cut away, and the remaining crystal melted and regrown. A repetition of this process can lead to the required ppt contamination levels of 238 U and 232 Th and ppb levels of potassium [71].…”

Increasing the sensitivity of LXe TPCs to dark matter by doping with helium or neon

“…When the expected larger signal yield is included, it should be relatively straightforward to identify the component created by the lighter element. Preliminary calculations based on the experience with SCENE and a similar measurement with NaI [31] suggest that even with the low doping fraction of He in LXe, adequate statistics on He recoils can be collected in a week-long run.…”