Neutron-Anti-Neutron Oscillation: Theory and Phenomenology

The discovery of neutrino masses has provided strong hints in favor of the possibility that B-L symmetry is an intimate feature of physics beyond the standard model. I discuss how important information about this symmetry as well as other scenarios for TeV scale new physics can be obtained from the baryon number violating process, neutron-anti-neutron oscillation. This article presents an overview of different aspects of neutron-anti-neutron oscillation and is divided into the following parts : (i) the phenomenon; (ii) the physics, (iii) plausible models and (iv) applications to cosmology. In particular, it is argued how the discovery of $n-\bar{n}$ oscillation can significantly affect our thinking about simple grand unified theory paradigms for physics beyond the standard model, elucidate the nature of forces behind neutrino mass and provide a new microphysical view of the origin of matter in the universe.Comment: 34 pages; 7 figures; Invited review for the issue on "Fundamental Neutron Physics" by J. Phys.