Pulse-shape discrimination between electron and nuclear recoils in a NaI(Tl) crystal

TL;DR

This study demonstrates improved pulse-shape discrimination in high light-output NaI(Tl) crystals, enhancing sensitivity to WIMP interactions and providing a comparison with DAMA/LIBRA's annual modulation results.

Contribution

It presents a novel measurement of pulse-shape discrimination power in NaI(Tl) crystals with high light output, and estimates WIMP detection sensitivity based on these results.

Findings

Enhanced pulse-shape discrimination due to high light output

Quantified discrimination power with a quality factor

Estimated WIMP detection sensitivity comparable to DAMA/LIBRA

Abstract

We report on the response of a high light-output NaI(Tl) crystal to nuclear recoils induced by neutrons from an Am-Be source and compare the results with the response to electron recoils produced by Compton scattered 662 keV $\gamma$-rays from a $^{137}$Cs source. The measured pulse-shape discrimination (PSD) power of the NaI(Tl) crystal is found to be significantly improved because of the high light output of the NaI(Tl) detector. We quantify the PSD power with a quality factor and estimate the sensitivity to the interaction rate for weakly interacting massive particles (WIMPs) with nucleons, and the result is compared with the annual modulation amplitude observed by the DAMA/LIBRA experiment. The sensitivity to spin-independent WIMP-nucleon interactions based on 100 kg$\cdot$year of data from NaI detectors is estimated with simulated experiments, using the standard halo model.