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

Conversions between neutrons n and Dark Matter candidate sterile neutrons n' have been proposed as a mechanism for Baryon Number ℬ violation. In the case that there is a small mass difference Δm 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 looking for anomalous neutron transmission through a strongly absorbing cadmium wafer inside of a 6.6 T magnet. The approach described here saw no regenerated neutrons above background, which provides an improved limit for neutron - sterile neutrons transformations for a range of Δm between 0.1 neV and 1000 neV.