Neutron detection and application with a novel 3D-projection scintillator tracker in the future long-baseline neutrino oscillation experiments

Neutrino oscillation experiments require a precise measurement of the neutrino energy. However, the kinematic detection of the final-state neutron in the neutrino interaction is missing in current neutrino oscillation experiments. The missing neutron kinematic detection results in a smaller detected neutrino energy than the true neutrino energy. A novel 3D-projection scintillator tracker, which consists of roughly ten million active cubes covered with an optical reflector, is capable of measuring the neutron kinetic energy and direction on an event-by-event basis using the time-of-flight technique thanks to the fast timing, fine granularity, and high light yield. The <math display="inline"><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>μ</mi></msub></math> interactions tend to produce neutrons in the final state. By measuring the neutron kinetic energy, the <math display="inline"><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>μ</mi></msub></math> energy can be reconstructed better, allowing a tighter incoming neutrino flux constraint. This article shows the detector’s ability to reconstruct neutron kinetic energy and the <math display="inline"><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>μ</mi></msub></math> flux constraint achieved by selecting the charged-current interactions without mesons or protons in the final state.