Ako Jamil successfully defends thesis, “Rare Event Searches in Liquid Xenon with EXO-200 and nEXO”

August 4, 2022

On July 26, 2022, Ako Jamil successfully defended the thesis: “Rare Event Searches in Liquid Xenon with EXO-200 and nEXO” (advisor: David Moore).

Jamil explained: “The neutrino is the most abundant massive particle in the universe and yet we still know very little about its properties. The Standard Model of Particle Physics assumes that neutrinos are massless and yet the definitive observation of neutrino oscillations shows that neutrinos must have a non-zero mass. However, its mass is very small and about six orders of magnitude smaller than the next lightest particle, the electron. Understanding the reason for the smallness of the neutrino masses as well as the observed matter-anti-matter asymmetry in the universe is the motivation to search for a hypothesized rare nuclear decay which is the neutrinoless double beta decay. If observed, it would show that neutrinos are their own anti-particles and would provide some of the key ingredients for getting a better understanding of the nature of neutrinos and possible answers to the above questions. nEXO is a tonne-scale liquid xenon based experiments searching for the neutrinoless double beta decay of Xe-136 with a half-life sensitivity as long as 10^28 years. Understanding the light and charge response of liquid xenon to ionizing radiation is key for maximizing the physics reach of the experiment.”

Jamil will be joining the Princeton Physics Department as a Robert H. Dicke Fellow to work on DarkSide-20k, which is an upcoming multi-tonne liquid argon dark matter experiment.

Thesis Abstract:

Liquid Xenon (LXe) detectors, operated as Time Projection Chambers (TPC), have emerged as a key technology in the past decades in the search for extremely rare events, such as the interaction of dark matter or neutrinoless double beta decay (0νββ) of Xe-136. These experiments need to operate in an ultra-low background regime. The remaining backgrounds need to be not only reliably and accurately modeled but can also be rejected using sophisticated reconstruction techniques that will distinguish signal from background. In this work, three generations of liquid xenon experiments are examined.
 
Data from the EXO-200 experiment was analyzed for a novel interaction mechanism of dark matter with ordinary matter via a charged-current absorption of fermionic dark matter.
 
A detailed understanding of the light and charge transport in liquid xenon for the upcoming tonne-scale nEXO experiment is described, including a robust estimate of the discovery and exclusion sensitivity for 0νββ in Xe-136.
 
Lastly, a conceptual design for a possible kilotonne-scale LXe detector is presented, which includes requirements on the photon detection system to enable novel Cherenkov and scintillation light separation for improved discrimination between β-like and ββ-like events.