Measuring the Neutrino Event Time in Liquid Argon by a Post-Reconstruction One-parameter Fit

Abstract

We propose a relatively simple method to measure the event time in liquid Argon (LAr) TPC-based neutrino detectors that takes advantage of the topological reconstruction of each event from the TPC data prior to performing a one-parameter fit. Measured times and positions of detected photons are fit to the expected pattern of light from the tracks as reconstructed using the electron drift. The event can be treated as a rigid body with only the neutrino interaction time as a free parameter. The optical properties of LAr are comparable to those of water for Cherenkov light in visible wavelengths. Data-Monte Carlo comparisons of the light patterns, given the known track topology from electron drift, enable in situ calibration of the optical model and further optimization of the timing. A back-of-the-envelope calculation predicts that the single parameter fit for the interaction time requires a significantly lower photodetector coverage than needed for the same precision in conventional warm-liquid detectors.