Nuclear Recoil Calibration in the LUX-ZEPLIN Experiment using a Deuterium-Deuterium Neutron Source

Calibrations for low-energy nuclear recoil (NR) events are essential for understanding the detector response to Boron-8 solar neutrinos and potential WIMP dark matter interactions in the LUX-ZEPLIN (LZ) experiment, an experiment that aims to primarily detect dark matter directly. To perform NR calibration, various sources are used, one of which is a 2.45 MeV monoenergetic neutron source produced by a Deuterium-Deuterium (DD) neutron generator. The DD neutrons are collimated into the LZ detector through horizontal and angled conduits. The energy of the neutrons can be reduced to 10-200 keV or 350±40 keV before injection by reflecting them off a hydrogen-loaded or a deuterium-loaded target, respectively. These lower incident neutron energies allow NR calibration of sub-keV recoils. In this presentation, I will describe the NR calibration performed in-situ in the LZ detector using direct DD neutrons, and the characterization of the detector performance using the neutron calibration data. I will also detail the techniques used to reduce the incident neutron energy, needed to probe recoil energy relevant for lower-mass dark matter candidates.