The Hybrid detector: A phonon-mediated iZip style detector for low mass Dark Matter search

Abstract

There are numerous evidences that support the existence of dark matter but there is no terrestial experiment which has yet been able to detect it. The nature of dark matter is still unknown and multiple candidates are proposed which can be a dark matter particle and can account for the cosmological evidences found till date.

There are multiple earth-based detection experiments like SuperCDMS, LUX etc. which look at the direct interaction of the dark matter particles with some standard model particle. Two big challenges faced by these type of experiments are the low energy threshold of the detectors to reach an energy range where they might be able to detect the dark matter signal and the ability to discriminate signal-like events from the plethora of background events in the detectors due to a variety of other sources.

SuperCDMS interleaved Z-sensitive Ionization and Phonon(iZIP) detectors have shown great success in discriminating electron recoils (the major background) and nuclear recoils (the signal-like events), while the High Voltage (HV) detectors have reached very low (a few eV) energy thresholds by sacrificing that discrimination. This thesis focuses on a novel phonon-mediated two-stage silicon detector that retains both an excellent threshold performance of the HV detector and maintain the iZIP-style background discrimination. Over multiple runs in the Nader's Test Facility and the MINER experiment at NSC, the detector characterization and testing was done with the first prototype Si detector which gave an encouraging result of clear discrimination between signal and background events. This new detector technology has the potential to significantly enhance the sensitivity to dark matter and coherent neutrino scattering experiments beyond the capabilities of current technologies that have limited discrimination at low energies.