Title: A New Method to Detect Neutron-Antineutron Oscillations with Very Efficient Use of Cold Neutron Beams

Abstract: Neutrons can oscillate into antineutrons when interactions are present which violate baryon number by two units, a feature of theories which also provide a mechanism for neutrinos to develop their observed masses and can explain the observed cosmological asymmetry between matter and antimatter.  We present a new method to experimentally probe neutron-antineutron oscillations using beams of free neutrons. Previous realizations of these experiments rely on the neutrons undergoing, ballistic flight while they oscillate, to ensure the “quasi-free” approximation is satisfied and the oscillation probability is not reduced by magnetic fields or interactions with matter. When magnetic fields or wall collisions are present, phase shifts develop between the neutron and antineutron which can damp out oscillations. Our method exploits properties of the quantum mechanical reflection of the neutron-antineutron wavefunction to utilize the whole cold neutron beam intensity produced at ILL, resulting in potential gains of orders of magnitude over the previous cold neutron beam measurements.