Minimal Models for Axion and Neutrino

The PQ mechanism resolving the strong CP problem and the seesaw mechanism explaining the smallness of neutrino masses may be related in a way that the PQ symmetry breaking scale and the seesaw scale arise from a common origin. Depending on how the PQ symmetry and the seesaw mechanism are realized, one has different predictions on the color and electromagnetic anomalies which could be tested in the future axion dark matter search experiments. Motivated by this, we construct various PQ seesaw models which are minimally extended from the (non-) supersymmetric Standard Model and thus set up different benchmark points on the axion-photon-photon coupling in comparison with the standard KSVZ and DFSZ models.Comment: 12 pages and 2 figures, references added, matched with the published version in PL

An extension of tribimaximal lepton mixing

Harrison, Perkins and Scott have proposed simple charged lepton and neutrino mass matrices that lead to the tribimaximal mixing $U_{\rm TBM}$. We consider in this work an extension of the mass matrices so that the leptonic mixing matrix becomes $U_{\rm PMNS}=V_L^{\ell\dagger}U_{\rm TBM}W$, where $V_L^\ell$ is a unitary matrix needed to diagonalize the charged lepton mass matrix and $W$ measures the deviation of the neutrino mixing matrix from the bimaximal form. Hence, corrections to $U_{\rm TBM}$ arise from both charged lepton and neutrino sectors. Following our previous work to assume a Qin-Ma-like parametrization $V_{\rm QM}$ for the charged lepton mixing matrix $V_L^\ell$ in which the {\it CP}-odd phase is approximately maximal, we study the phenomenological implications in two different scenarios: $V_L^\ell=V_{\rm QM}^\dagger$ and $V_L^\ell=V_{\rm QM}$. We find that the latter is more preferable, though both scenarios are consistent with the data within $3\sigma$ ranges. The predicted reactor neutrino mixing angle $\theta_{13}$ in both scenarios is consistent with the recent T2K and MINOS data. The leptonic {\it CP} violation characterized by the Jarlskog invariant $J_{\rm CP}$ is generally of order $10^{-2}$.Comment: 20 pages and 8 figures, Accepted in Phys.Review