Backgrounds In The LZ Dark Matter Experiment

LUX-ZEPLIN (LZ) is a dark matter experiment employing a 7 tonnes active volume of liquid xenon in a dual-phase time projection chamber (TPC), surrounded by an instrumented xenon “skin” region and a gadolinium-loaded liquid scintillator outer detector that primarily serve as active vetoes for gamma-ray and neutron backgrounds, respectively. A comprehensive material assay and selection campaign for detector components, along with a xenon purification campaign, have further ensured an ultra-low background environment. These mitigations allow LZ to have a projected sensitivity to WIMP-nucleon spin-independent cross section of 1.4 x 10^-48 cm² for a 40 GeV/c² mass WIMP over a 1000 day livetime using a quiet 5.6 tonnes fiducial volume. In order to achieve such unprecedented sensitivity to dark matter, it is critical to understand the backgrounds present in the detector. This talk will provide an overview of backgrounds in the LZ detector with an emphasis on techniques to constrain these backgrounds in situ. The implications of a well-constrained background model on the LZ sensitivity will also be discussed.