Improved Limits on n → n' Transformation from the Spallation Neutron Source

Conversions between neutrons n and a Dark Matter mirror neutron n′ has been proposed as a

mechanism for Baryon Number B violation.

In the case that there is a small mass difference Δm or energy difference ΔE between the n and the n′ states, oscillations can be induced by compensating for Δm with a magnetic field.

A search for such neutron oscillations was performed at the Spallation Neutron Source by placing a thin cadmium wafer inside of 6.6 T magnet.

The approach described here saw no regenerated neutrons above background, which provides a new limit for neutron - mirror neutrons transformations for a range of Δm between about 0.1 neV and ~1000 neV.