LZ Dark Matter Search

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of known particles. Deciphering the nature of this so-called Dark Matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. A leading hypothesis is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, that were produced moments after the Big Bang. If WIMPs are the dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei in detectors located deep underground to help reject backgrounds due to cosmic rays. LZ is a ~7-tonne liquid xenon (LXe) dark matter detector to be installed at the 4850-foot level of the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to look for dark matter. This work will contribute to the design of that detector. Development of technology related to LXe will find use in the increasing number of experiments worldwide using noble liquids as detection materials. These projects will also result in technical training in radiation detection, cryogenics, and gas purification for graduate and undergraduate students. LXe has practical applications to gamma ray imaging for astrophysics, Homeland Security, and medical imaging. This detector will use established liquid xenon time projection chamber technology with readout of primary and secondary scintillation signals for particle identification, together with 3-D position reconstruction to exploit the self-shielding of the liquid xenon, removal of surface artifacts, and calibration of position-dependent response functions. The design also features a gadolinium-loaded liquid scintillator veto that will hermetically enclose the central xenon detector and provide powerful tagging of background neutrons and gammas. The LZ experiment will have world-leading sensitivity to WIMP dark matter with a sensitivity about 400 times better than current results and covering a substantial range of theoretically motivated candidates. This award will provide funding to enable this research group to continue to contribute to the LZ dark matter experiment with work on the cathode high voltage delivery system.