Further search for magnetic-field-induced neutron disappearance in an ultracold neutron beam

Abstract

We report the results of the second iteration of an experiment searching for neutron-hidden-neutron oscillations in a beam of ultracold neutrons, conducted at the PF2 facility of the Institut Laue Langevin (ILL). Oscillations were tested via neutron disappearance as a function of an applied magnetic field, in the context of a phenomenological two-parameter model assuming zero hidden potentials. The magnetic field was varied in a step-wise manner in order to resonantly enhance the oscillation probability at different mass splittings ($\delta m$) across a 60--1550 peV range. No evidence for neutron disappearance is observed and conservative limits on the neutron-hidden-neutron oscillation period ($\tau_{nn'}$) have been set at 95 % confidence level: $\tau_{nn'} > 200$ms for $|\delta m| \in [60, 400]$ peV and $\tau_{nn'} > 100$ ms for $|\delta m| \in [400, 1550]$ peV