Fast Neutron Measurements at the Fermilab Booster Neutrino Beam for a Coherent Elastic Neutrino Nucleus Scattering (CENNS) Experiment

Low energy neutrinos ($<$ 50 MeV) can engage in coherent elastic scattering with low momentum transfer on nuclear targets. Coherent scattering is important in supernovae, low-$Q^2$ probes of nuclear form factors, and low-energy tests of the Standard Model. Despite the largest low-energy neutrino cross section, it has remained unobserved because of its low energy deposition and neutron backgrounds. The CENNS collaboration proposes to deploy a 1-ton-scale, single-phase, liquid argon scintillation detector near the Fermilab Booster Neutrino Beam (BNB) for a first measurement. By placing the detector near the beam target far off-axis, a low-energy flux of stopped-pion neutrinos is produced. The proximity to the BNB produces beam-correlated neutron backgrounds whose elastic scatters are indistinguishable from the neutrino signal. In this talk, I will describe CENNS and our previous neutrons measurements near the BNB. I will also highlight our current campaign to map the neutron energy and direction spectrum at the BNB while modulating a series of concrete neutron shields around our neutron detectors. The results will be used to design a neutron shield for a first CENNS measurement.