Large Area Picosecond Photodetector in Accelerator Neutrino Neutron Interaction Experiment

The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a 26-ton water Cherenkov experiment operating on the Booster Neutrino Beamline at Fermilab. ANNIE aims to measure the neutron yield from neutrino-nucleus interactions as a function of lepton kinematics to reduce systematic uncertainties in future long baseline neutrino oscillation experiments. ANNIE is also a test bed for novel detector technologies including LAPPDs, whose precision timing and imaging capabilities are expected to improve the reconstruction of the lepton and the neutrino interaction vertex. ANNIE has achieved the first successful detection of muon neutrino interactions using an LAPPD. We show preliminary results of vertex reconstruction using LAPPD with forward folding method. We illustrate the LAPPD's imaging and track reconstruction capabilities for Cherenkov radiation in neutrino experiments.