$n-n'$ Oscillations: Sensitivity of a first UCN beam experiment

TL;DR

This paper evaluates the potential sensitivity of a neutron beam experiment using ultra-cold neutrons and magnetic fields to detect oscillations into hidden sector particles, filling a gap in experimental tests across certain parameter ranges.

Contribution

It presents a novel experimental setup and sensitivity analysis for neutron hidden neutron oscillations at intermediate mass-splitting using magnetic fields.

Findings

Predicted sensitivity on oscillation time of a few seconds.

Utilized a novel UCN counter at ILL for beam flux monitoring.

Identified experimental parameters influencing detection sensitivity.

Abstract

Oscillations of the neutron into a hidden sector particle are processes predicted in various Standard Model extensions. This extra channel for neutron disappearance has not been tested experimentally in large portions of the oscillation parameter space. Several efforts have been recently made on revising the oscillation time limits at low mass-splitting in ultra-cold neutron (UCN) storage experiments, and at larger mass-splitting in passing-through-wall experiments. In this work, we present the expected sensitivity of an experiment searching for neutron hidden neutron oscillations at intermediate mass-splitting via the application of magnetic fields in the range $B_0=30-1100$ $\mu$T. This experiment was performed at the Institut-Laue-Langevin using a novel UCN counter to monitor the beam flux. The measured UCN rate and the data collection technique predict a sensitivity on the oscillation time at the level of a couple of seconds.