Modeling the low-energy accidental coincidence background in the LUX-ZEPLIN experiment

The LUX-ZEPLIN (LZ) experiment has placed world-leading limits on WIMP-nucleon scattering cross sections for masses above 9 GeV/c^2. LZ consists of a dual-phase liquid xenon TPC, which detects both scintillation photons (S1) and ionization electrons (S2) from particle interactions. Extending the search to lower WIMP masses requires robust modeling of low-energy detector backgrounds, which can mimic signals from dark matter and expected 8B solar neutrinos. The dominant background in this regime comes from accidental coincidences of "isolated" S1- and S2-like pulses, which are produced by various instrumental effects. In this presentation, I will show how careful consideration of these effects allows for improved modeling of the accidental coincidence background in LZ, and present a series of model validations that demonstrate excellent agreement with data down to keV recoil energies. The accuracy of this model is crucial in maximizing the sensitivity of LZ to low-mass WIMP candidates and 8B.