Demonstration of neutron identification in neutrino interactions in the MicroBooNE liquid argon time projection chamber

TL;DR

This paper demonstrates a new method for identifying neutrons produced in neutrino interactions within a liquid argon detector, improving the understanding of missing energy in neutrino oscillation measurements.

Contribution

The paper introduces the first technique to tag neutrino-induced neutrons in liquid argon time projection chambers, validated with MicroBooNE data.

Findings

60% of selected tracks are neutron-induced secondary protons

Method successfully identifies neutrino-induced neutrons

Validated with a subset of MicroBooNE data

Abstract

A significant challenge in measurements of neutrino oscillations is reconstructing the incoming neutrino energies. While modern fully-active tracking calorimeters such as liquid argon time projection chambers in principle allow the measurement of all final state particles above some detection threshold, undetected neutrons remain a considerable source of missing energy with little to no data constraining their production rates and kinematics. We present the first demonstration of tagging neutrino-induced neutrons in liquid argon time projection chambers using secondary protons emitted from neutron-argon interactions in the MicroBooNE detector. We describe the method developed to identify neutrino-induced neutrons and demonstrate its performance using neutrons produced in muon-neutrino charged current interactions. The method is validated using a small subset of MicroBooNE's total dataset. The selection yields a sample with $60\%$ of selected tracks corresponding to neutron-induced secondary protons.