New high-sensitivity search for neutron to mirror-neutron oscillations at the PSI UCN source

TL;DR

This study conducted a high-sensitivity search for neutron to mirror-neutron oscillations at PSI, using magnetic field scans and simulations, finding no evidence and setting new exclusion limits on the oscillation parameters.

Contribution

It provides the first comprehensive high-sensitivity experimental search excluding previous claimed signals for neutron to mirror-neutron oscillations.

Findings

No evidence of neutron to mirror-neutron oscillations was observed.

New limits on the oscillation time constant were established.

The parameter space claimed by previous anomalies was excluded with 99.98% confidence.

Abstract

In a search for potential signals of neutron (n) to mirror-neutron (n') oscillations, a collaboration centered at the Paul Scherrer Institute (PSI) investigated the remaining parameter space claimed by anomalies with a dedicated high-sensitivity apparatus. An elaborate magnetic-field-mapping analysis and Monte Carlo simulation of the cumulative n-n' oscillation probabilities along the neutron trajectories inside the storage vessel complemented the neutron data analysis. Magnetic fields were scanned in the range 5 microT < B < 109 microT. No evidence of anomalous neutron losses was found. Consequently, new limits for the n-n' oscillation time constant were set. The parameter space, previously claimed for potential signals, has been excluded to 99.98 %.