μ-τ symmetry and radiatively generated leptogenesis

We consider a mu-tau symmetry in neutrino sectors realized at the GUT scale in the context of a seesaw model. In our scenario, the exact mu-tau symmetry realized in the basis where the charged lepton and heavy Majorana neutrino mass matrices are diagonal leads to vanishing lepton asymmetries. We find that, in the minimal supersymmetric extension of the seesaw model with large tan beta, the renormalization group (RG) evolution from the GUT scale to seesaw scale can induce a successful leptogenesis even without introducing any symmetry breaking terms by hand, whereas such RG effects lead to tiny deviations of theta(23) and theta(13) from pi/4 and zero, respectively. It is shown that the right amount of the baryon asymmetry eta(B) can be achieved via so-called resonant leptogenesis, which can be realized at rather low seesaw scale with large tan beta in our scenario so that the well-known gravitino problem is safely avoided.