2026 Theses Doctoral

Search for Particle Dark Matter with XENONnT: From Weakly Interacting Massive Particles to Sub-Proton-Mass Candidates

Shi, Shenyang

The XENONnT experiment, located at the Laboratori Nazionali del Gran Sasso, is designed primarily to search for weakly interacting massive particles (WIMPs). Using data collected between 2021 and 2025, this thesis presents three complementary dark matter searches spanning masses from 30 MeV to 1 TeV. The first targets WIMPs between 12 GeV and 1 TeV, with a systematic treatment of neutron-related analyses, including nuclear recoil calibration and radiogenic neutron background modeling and mitigation. The second searches for light dark matter between 3 and 12 GeV, developing dedicated methods to mitigate accidental coincidence backgrounds for the first dark matter search approaching the solar neutrino fog. The third searches for light dark matter from 30 MeV to 12 GeV, as well as axion-like particles and related candidates, using a complete ionization-only background model developed for XENONnT. No significant excess above the expected background is observed, and competitive limits are placed on a broad range of dark matter models.