Public Material:  A Search for Low-mass Dark Matter via Bremsstrahlung Radiation and the Migdal Effect in SuperCDMS

This Public Documentation accompanies the results on the search for inelastically scattering dark matter (DM) in SuperCDMS. Two signal channels were considered: Bremsstrahlung radiation of a photon from a recoiling nucleus, and an electron ejected from an atom via the Migdal Effect. These byproducts of inelastic nuclear recoils allow for the measurement of a signal from sub-GeV DM that would otherwise result in an elastic recoil energy that is below the energy threshold of the detector. The Bremsstrahlung channel does not exclude any new parameter space, but the Migdal channel results in a world-leading limit of DM-nucleon cross-section for DM mass below 0.1 GeV/c2.
These results are published in arXiv : 2302.09115

Public Material:  Ionization yield measurement using photo-neutron sources in Germanium CDMSlite detectors

This public documentation page is meant to supplement the work on the ionization yield measurement using photo-neutron sources in Germanium CDMSlite detectors. The study measures ionization yield for low energy nuclear recoils using Antimony-Beryllium(maximum recoil energy of 1.3 keV) and Yttrium-Beryllium(maximum recoil energy of 8.1 keV) photo-neutron sources. The Germanium detectors were part of the SuperCDMS Soudan setup and operated in the CDMS low ionization threshold experiment(CDMSlite) mode. This work aims to formulate a modified Lindhard model that works best for SuperCDMS detectors. This is done by fitting nuclear recoil spectra from GEANT4 simulations using a likelihood method to data collected from this dedicated calibration run(calibration of recoil energy to ionization yield). An accurate understanding of the nuclear recoil scale is necessary for reducing a major systematic uncertainty on the WIMP-nucleus scattering cross section limit
These results are published in arXiv : 2202.07043

Public Material: CPD DM search

This Public Documentation accompanies the results of nuclear-recoiling dark matter search at the SLAC surface facility, using data taken with the Cryogenic PhotoDetector (CPD). The LAPDCPD is a Si wafer with a single distributed channel of W TESs for collection of athermal phonons. The detector has a 45.6 cm2 surface area, a 1 mm thickness, and a mass of 10.6 g. During this run, roughly 22 hours of science data was acquired. After applying simple cuts and using a well-motivated signal model, the resulting exclusion limit for DM-nucleus scattering is given below, alongside other plots approved for public release.
These results are published in Phys. Rev. Lett. 127, 061801

Public Material: HVeV Run 2

This Public Documentation accompanies the results on electron-recoiling dark matter (ERDM) from a 3 week long run of a 1g HVeV detector in the Northwestern ADR. During this run, one week of data (roughly 12 hours per day for 7 days) was acquired at 100V bias with a charge resolution of 0.03 electron-hole pairs, and 3 days at 60V with a resolution of 0.05 electron-hole pairs. Co-57 and laser calibrations were acquired, and a 0V control sample was also acquired over multiple days. The resulting limits for DM-electron scattering and DM absorption are given below, along with plots approved for public release.
These results are published in Phys. Rev. D 102, 091101(R)

Public Material: CDMSlite Run 2 period 1 LIPs Search

his Public Documentation accompanies the results of the search for Lightly Ionizing Particles (LIPs) using CDMSlite Run 2 period 1 data. The analysis is looking for LIPs of mass 5 MeV/$c^2$ to 100 TeV/$c^2$, charge e/100 to e/10$^8$, and $\beta\gamma$ 0.1 to 10$^6$. Geant4 simulation is used to create the probability distribution functions (PDFs) for LIPs of different charges, mass and $\beta\gamma$. The analysis efficiencies will be the same as the CDMSlite WIMP search with two additional correction factors to account for an additional source of inefficiency in singles and radial cuts. These factors arise due to the fact that unlike WIMPs, LIPs are capable of multiple detector interactions as well as multiple interactions within same detector. These correction factors are calculated using data from Geant4 simulation. The analysis is exploring new LIPs parameter space.
These results can be found at Phys. Rev. Lett. 127, 081802.

Public Material: Dark Absorption in SuperCDMS Soudan

Using data from CDMSlite (Runs 2 and 3) and select iZIP detectors from the SuperCDMS experiment at the Soudan Underground Laboratory, upper limits on the axioelectric coupling of axion-like particles (ALPs) and the kinetic mixing parameter of dark photons (DPs) are set. The analysis is based on Poisson statistics and assumes the respective particles constitute all of the galactic dark matter.

Public Material: HVeV Run1: Updated DM-Electron Scattering Cross Section Limits

We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 gram CDMS HV device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 MeV/c². We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 gram days). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations.