Final results of a search for free neutron-antineutron oscillations

Abstract

The final analysis of the data collected in a search for free $$n - \bar n$$ oscillations is presented. The experiment has been carried out at the Triga Mark II reactor of the Pavia University. A thermal neutrons current of 3.2·1010s−1 propagates in a quasi-free condition for an average time of flight of 8ms and impinges on two thin targets. The possible antineutron annihilation products would be detected in the first target. The second target works as a monitor of the background. No evidence for $$n - \bar n$$ transitions is found. A lower limit of 4.9·105s (90% c.l.) has been reached, with «zero» signal and with «zero» background events.