DEPARTMENT OF PHYSICS DISSERTATION: Samuel Wong

Ph.D. Candidate:  Samuel Wong

Research Advisor:  Peter Graham

Date:  Friday, April 18, 2025 

Time:  10:00 am PT

Location: Physics and Astrophysics Building, room 102/103 (PAB102/103)

Zoom link:  https://stanford.zoom.us/j/93765433540

Password: Email physicsstudentservices [at] stanford.edu (physicsstudentservices[at]stanford[dot]edu) for password.

Title:  Novel Searches for New Physics in Neutrino Detectors and at the LHC

Abstract:  I present two innovative strategies for detecting new physics: searching for decay signals from inelastic dark matter in neutrino detectors, and recovering long-lived particles trapped in LHC detector materials.

Inelastic dark matter, such as the Higgsino, with large mass splittings evades conventional WIMP direct detection but can produce distinctive photon signals in large neutrino detectors like JUNO, following upscattering in the Earth and subsequent decay. I show that an enhanced high-velocity tail of the dark matter distribution due to the Large Magellanic Cloud improves the sensitivity of this method, and that adding a large volume of heavy elements, such as lead or uranium, around the detector could further take advantage of this effect.

Additionally, TeV-scale long-lived particles with lifetimes of years or longer, such as gluinos in split supersymmetry, could have been copiously produced at the LHC yet escaped detection due to backgrounds, and may remain trapped in detector materials. I show that these trapped particles can be recovered from detector materials once prepared in liquid form, whether by melting silicon detectors, extracting liquid argon from electromagnetic calorimeters, or constructing a large water pool near ATLAS. These liquid samples can then be processed using iterative centrifugation followed by time-of-flight mass spectrometry, enabling single-particle sensitivity in macroscopic samples.