Search for mirror neutrons at ORNL*

The possibility that the neutron might transform into a sterile, mirror neutron has been proposed as a solution to questions such as the nature of dark matter and origin of the matter-antimatter asymmetry and has been linked to anomalies such as the neutron lifetime puzzle. We have conducted searches for neutrons transforming into mirror neutrons with a small mass difference using the Magnetism Reflectometer instrument at the Spallation Neutron Source. A first measurement has excluded the possibility that this phenomenon could explain the neutron lifetime anomaly. We will present improved limits from a second experimental search at the SNS with significantly reduced backgrounds and improved understanding of the neutron flux.