Determination of muon momentum in the MicroBooNE LArTPC using an improved model of multiple Coulomb scattering

We discuss a technique for measuring a charged particle's momentumby means of multiple Coulomb scattering (MCS) in the MicroBooNE liquid argon time projection chamber(LArTPC). This method does not require the full particle ionization track to be contained inside of the detector volume as other track momentumreconstruction methods do (range-based momentumreconstruction and calorimetric momentumreconstruction). We motivate use of this technique, describe a tuning of the underlying phenomenological formula, quantify its performance on fully contained beam-neutrino-induced muontracks both in simulation and in data, and quantify its performance on exiting muontracks in simulation. We find agreement between data and simulation for contained tracks, with a small bias in the momentumreconstruction and with resolutions that vary as a function of track length, improving from about 10% for the shortest (one meter long) tracks to 5% for longer (several meter) tracks. For simulated exiting muonswith at least one meter of track contained, we find a similarly small bias, and a resolution which is less than 15% for muonswith momentumbelow 2 GeV/c.