Date of Award
Orin Harris, Ph.D.
Bubble chambers are one of several detector types that particle physicists use to search for the as-yet-undetected dark matter. The PICO collaboration – formed from the merger of the similar PICASSO and COUPP experiments – runs such a bubble detector using superheated fluorocarbons (with and without iodine). Bubbles that form along chamber walls exhibit different behavior than those which nucleate in the bulk of the target liquid due to shape distortions from the wall boundary; in previous analyses when searching for dark matter, these wall events have been cut from the data to control for the differing behavior using information available from images or pressure rise data. Seventy-nine events of dark matter search data acquired by the PICO-60 bubble chamber in 2016 were visually categorized as wall or bulk events and analyzed acoustically. Wall events were found to significantly differ from bulk events using multiple acoustic parameters including overall loudness. Acoustic data was found to be a promising indicator of event type and yielded an efficient and reliable fiducial cut (100% specificity with up to 92% efficiency), likely allowing for a larger volume of target fluid to be considered in future analyses. Having multiple modes of observation is also critical in validating existing methods of fiducialization. The preliminary results indicate that future analyses would likely showcase several percent more efficient fiducialization by leveraging acoustic handles similar to those investigated here.
Volkova, Lucia, "Acoustic Parameters as Discriminators of Wall Events in PICO Dark Matter Search Data" (2021). University Honors Program Senior Projects. 26.