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.