Speaker
Description
Rare event searches, such as those targeting dark matter interactions and neutrinoless double beta decay (0νββ), face challenges from gamma-rays originating in rock, contributing to electron recoil background. This report presents a dual investigation: measurements of natural radioactivity in rock samples from Boulby Mine and a simulation assessing shielding thickness for a future detector. The measurements provide data for normalising conditions in prospective experiments at Boulby. The simulation studies the effectiveness of water shielding around a detector, focusing on the Weakly Interacting Massive Particle (WIMP) energy range (0 – 20 keV) and the energy range near the 0νββ Q-value (2.458 MeV for Xe-136).
The study design features a simplified xenon-based detector with a 70-tonne active mass, encompassed by veto systems and water shielding. Our findings indicate that the gamma-ray background from rock is unlikely to persist through analysis cuts in the WIMP energy range with water/scintillator thickenss of > 3 m thanks to a powerful discrimination between potential WIMP signals and gamma-ray background. For 0νββ decay signal searches fiducial mass of the detector may need to be reduced to keep the background from rock below 1 event in 10 years of running.
