Deviations from Tri-bimaximal Neutrino Mixing in Type-II Seesaw and Leptogenesis

Understand

Current experimental data allow the zero value for one neutrino mass, either m_1 = 0 or m_3 = 0.

• This observation implies that a realistic neutrino mass texture can be established by starting from the limit (a) m_1 = m_2 = 0 and m_3 \neq 0 or (b) m_1 = m_2 \neq 0 and m_3 = 0.
• In both cases, we may introduce a particular perturbation which ensures the resultant neutrino mixing matrix to be the tri-bimaximal mixing pattern or its viable variations with all entries being formed from small integers and their square roots.
• We find that it is natural to incorporate this kind of neutrino mass matrix in the minimal Type-II seesaw model with only one heavy right-handed Majorana neutrino N in addition to the SU(2)_L Higgs triplet \Delta_L.