Neutron Background in XENONnT

XENONnT uses a two-phase liquid xenon time projection chamber (LXeTPC) to search for dark matter, primarily Weakly Interacting Massive Particles (WIMPs). Like WIMPs, neutrons produce a similar signature of nuclear recoils and thus represent the ultimate background in a search for WIMPs. On the other hand, while WIMPs are expected to scatter only once in the detector, neutrons will suffer multiple scatters and can thus be recognized in a large position-sensitive detector such as the XENONnT TPC. As a consequence, the neutron background can be significantly suppressed with multiple-scatter neutron tagging techniques based on the signal waveform and PMT patterns. In this talk, I will present the prediction and rejection techniques for neutron background in XENONnT with validation from Geant4 simulation and AmBe neutron calibration.