Please join us:
Joel Fuentes’ PhD Thesis Defense
Wednesday, August 18, 2021, 9:00 am CDT
RESPONSE OF SUPERHEATED C3F8 AND C2H2F4 TO NUCLEAR AND ELECTRON RECOILS: APPLICATIONS TO DARK MATTER DETECTION
The PICO-500 bubble chamber will search for Weakly Interacting Massive Particles (WIMPs) at the SNOLAB underground laboratory. This dark matter detector is expected to reach spin-dependent WIMP-nucleus cross-sections of ≈10-42cm2, furthering PICO’s present leadership in sensitivity to this type of coupling. Its prototype, PICO-40L, is presently operating in the same underground location. The GUNTER calibration bubble chamber, designed and assembled at the University of Chicago as part of this thesis, was operated using C3F8 and C2H2F4 (refrigerant R-134a) within its 25 c.c. active volume. These compounds are favored as WIMP scattering targets for dark matter direct detection. This thesis reports on high-statistics calibration studies from a C3F8 and R-134a filled GUNTER, aiming to confirm the sensitivity of these targets to WIMP scattering, inform upgrades in acoustic sensor design for PICO-500, find possible indications of acoustic discrimination between electron and nuclear recoils, and define optimal target run conditions for PICO-40L and PICO-500. GUNTER calibration data are also used to demonstrate a new model of bubble-nucleation by electron-recoils, casting light on the underlying physical mechanisms at work. The hydrogenated target R-134a, of interest for low-mass WIMP detection, was also studied for the first time in this role, defining the parameters that describe its response to nuclear and electron recoils.
Juan I. Collar (Chair)
Joel will be joining Bank of America in September as a Quantitative Financial Analyst, Associate VP in the Consumer Risk Modeling and Delivery (CRMD) team.