Total Neutron Cross Section Measurement with a 3D Projection Scintillator Tracker for Long-baseline Neutrino Experiments:*

The long-baseline neutrino oscillation experiments depend on detailed models of neutrino interactions on nuclei. However, these models constitute an important source of systematic uncertainty partly due to the missing information of the final state neutrons in the detectors to date. As such, neutron information is desired in the near detectors of upcoming long-baseline neutrino experiments. Here, we are proposing a three-dimensional projection scintillator tracker to be used as a near detector component in the next generation long-baseline neutrino experiments such as T2K upgrade and DUNE. Due to the good timing resolution and fine granularity, this technology is capable of measuring neutron kinetic energy from neutrino interactions and can provide valuable data for refining neutrino interaction models and better reconstruct the neutrino energy. Neutron beam data has been taken in Los Alamos National Lab (LANL) in both 2019 and 2020 with neutron energy ranging from 0 to 800 MeV using two of such prototype detectors. In order to demonstrate the capability of the neutron detection, a total neutron-scintillator cross section is measured with one of the prototypes and compared to external measurements. In this presentation, the details of the cross section measurement and the systematic uncertainty handling will be presented.