Observable Neutron–Antineutron Oscillations in Seesaw Models of Neutrino Mass

We show that in a large class of supersymmetric models with spontaneously broken B − L symmetry, neutron–antineutron oscillations occur at an observable level even though the scale of B − L breaking is very high, vB−L ∼ 2 × 10 16 GeV, as suggested by gauge coupling unification and neutrino masses. We illustrate this phenomenon in the context of a recently proposed class of seesaw models that solves the strong CP problem and the SUSY phase problem using parity symmetry. We obtain an upper limit on N − N̄ oscillation time in these models, τN−N̄ ≤ 10 −10 sec. This suggests that a modest improvement in the current limit on τN−N̄ of 0.86×10 8 sec will either lead to the discovery of N − N̄ oscillations, or will considerably restrict the allowed parameter space of an interesting class of neutrino mass models.