Light Dark Matter Constraints from a SuperCDMS Cryogenic Silicon Detector with Single-Charge Sensitivity

Astrophysical observations suggest that the universe contains a substantial amount of dark matter, likely composed of particles beyond the Standard Model. The SuperCDMS (Cryogenic Dark Matter Search) SNOLAB experiment is a next-generation direct detection effort using cryogenic germanium and silicon detectors to measure phonon and ionization signals from dark-matter recoils. It aims to improve sensitivity to dark-matter particles with masses below 10 GeV by an order of magnitude. As part of this effort, HVeV detectors (high voltage eV scale), which are gram scale with single-charge sensitivity, serve as a prototype to provide insight into detector response, calibration methods and background sources. Three prior HVeV runs have yielded competitive constraints on low-mass dark matter. This dissertation analyzes data from the HVeV Run 4 experiment, conducted in an underground laboratory at Northwestern University. The experiment benefits significantly from the identification and elimination of the luminescence from the printed circuit boards in the detector holder used in Run 3, resulting in a lower background event rate and stronger constraints. Data from 10.80 gram-days of exposure were analyzed in a blinded study using a likelihood-based method. Limits are set on the dark matter-electron scattering cross-section in the mass range of MeV to GeV, dark photon absorption mixing parameter and axion-like particle coupling constant in the mass range of eV to tens of eV. The results turn out to be competitive and world-leading in some of the lower mass ranges. The experiment also provides information on potential background sources in the low-energy range, where future HVeV runs are expected to reduce or model them.

Department dc:contributor.department

Physics

Year dc:date.issued

2025

Author dc:creator

• Zhang, Enze

Advisor dc:contributor.advisor

• Diamond, Miriam

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Handle dc:identifier.uri

https://hdl.handle.net/1807/142665

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/142665