Observational Cosmology Seminar

The particle nature of dark matter remains one of the last open questions in physics. I will briefly introduce some current theoretical models such as asymmetric dark matter and dark-sector models that motivate searches below the classic WIMP scale. For over 30 years the Cryogenic Dark Matter Search experiment has pursued the direct detection of dark matter. Its current iteration, SuperCDMS SNOLAB is currently operating phonon-mediated silicon and germanium detectors at milli-Kelvin temperatures, 2 km underground. Our goal is to search for dark matter in the 0.5–5 GeV/c² mass range, with projected world-leading sensitivity to nucleon-coupled dark matter. Background modeling and mitigation are crucial for our analysis.. In this talk I will present my work on two fronts. First I will introduce direct detection of dark matter and the SuperCDMS experiment. For this we are developing a flexible Python framework for the dark matter search itself: profile-likelihood fits of signal and background models that fold in detector response, resolution, and yield uncertainties to produce sensitivity projections and, ultimately, limits. Then I'll talk about BBRsim, an end-to-end simulation of the blackbody radiation emitted by the warmer stages of the cryostat in the experiment. These mm-wave photons leak through flange gaps and cable slots whose dimensions are comparable to the photon wavelength, so their propagation is diffractive and beyond the reach of ray-tracing codes. Left unmodeled, this radiation loads our transition-edge sensors and degrades detector thresholds; in superconducting qubits it is a known quasiparticle-poisoning channel. BBRsim embeds full-wave ANSYS HFSS solutions of each aperture into Geant4 as a probabilistic boundary process, tracking both the wave-like and particle-like propagation of thermal photons through a full cryostat geometry. I will show the first validation results and our planned experimental validation program.