Measurement of the Transverse and Longitudinal Diffusion of Ionization Electrons in Liquid Argon with the ICARUS Detector

Neutrino experiments using liquid argon time projection chambers (LArTPCs) have shown that the smearing of ionization signal waveforms by diffusion can have a significant impact on particle identification and energy reconstruction. Understanding and accounting for diffusion effects can improve the accuracy and precision of measurements in these detectors. Previous measurements have been made for the longitudinal diffusion constant in liquid argon near a drift electric field of 500 V/cm, where many LArTPC neutrino experiments operate. However, no measurements of transverse diffusion in liquid argon have been made at similar drift electric field values. We present a novel method making use of the relative change in ionization signal waveforms between near-anode and near-cathode data collected using a LArTPC, allowing for the longitudinal and transverse diffusion constants to be measured simultaneously and precisely. First studies using Monte Carlo simulation and data collected with the ICARUS detector, operating at a drift electric field of 493.8 V/cm, are presented. Notably, our measurement of the transverse diffusion constant in liquid argon at ICARUS is the first of its kind near this value of drift electric field.