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Register a new userRelatively Large Theta13 from Modification to the Tri-bimaximal, Bimaximal and Democratic Neutrino Mixing Matrices
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Inspired by the recent T2K indication of a relatively large theta_{13}, we provide a systematic study of some general modifications to three mostly discussed neutrino mixing patterns, i.e., tri-bimaximal, bimaximal and democratic mixing matrices. The correlation between theta_{13} and two large mixing angles are provided according to each modifications. The phenomenological predictions of theta_{12} and theta_{23} are also discussed. After the exclusion of several minimal modifications, we still have reasonable predictions of three mixing angles in 3 Sigma level for other scenarios.
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In this work we analyze the corrections to tribimaximal (TBM), bimaximal (BM) and democratic (DC) mixing matrices for explaining large reactor mixing angle $theta_{13}$ and checking the consistency with other neutrino mixing angles. The corrections are parameterized in terms of small orthogonal rotations (R) with corresponding modified PMNS matrix of the form $R_{ij}cdot U cdot R_{kl}$ where $R_{ij}$ is rotation in ij sector and U is any one of these special matrices. We showed the rotations $R_{13}cdot U cdot R_{23}$, $R_{12}cdot U cdot R_{13}$ for BM and $R_{13}cdot U cdot R_{13}$ for TBM perturbative case successfully fit all neutrino mixing angles within $1sigma$ range. The perturbed PMNS matrix $R_{12}cdot U cdot R_{13}$ for DC, TBM and $R_{23}cdot U cdot R_{23}$ for TBM case is successful in producing mixing angles at 2$sigma$ level. The other rotation schemes are either excluded or successful in producing mixing angles at $3sigma$ level.
We propose an extension of tri-bimaximal mixing to include a non-zero reactor angle $theta_{13}$ while maintaining the tri-bimaximal predictions for the atmospheric angle $theta_{23}=45^o$ and solar angle $theta_{12}=35^o$. We show how such tri-bimaximal-reactor mixing can arise at leading order from the(type I) see-saw mechanism with partially constrained sequential dominance. Partially constrained sequential dominance can be realized in GUT models with a non-Abelian discrete family symmetry, such as $A_4$, spontaneously broken by flavons with a particular vacuum alignment.
We construct a model for tri-bimaximal lepton mixing which employs only family symmetries and their soft breaking; neither vacuum alignment nor supersymmetry, extra dimensions, or non-renormalizable terms are used in our model. It is an extension of the Standard Model making use of the seesaw mechanism with five right-handed neutrino singlets. The scalar sector comprises four Higgs doublets and one complex gauge singlet. The horizontal symmetry of our model is based on the permutation group S_3 of the lepton families together with the three family lepton numbers--united this constitutes a symmetry group Delta(6infty^2). The model makes no predictions for the neutrino masses.
We study corrections to tri-bimaximal (TBM) neutrino mixing from renormalization group (RG) running and from Planck scale effects. We show that while the RG effects are negligible in the standard model (SM), for quasi-degenerate neutrinos and large $tanbeta$ in the minimal supersymmetric standard model (MSSM) all three mixing angles may change significantly. In both these cases, the direction of the modification of $theta_{12}$ is fixed, while that of $theta_{23}$ is determined by the neutrino mass ordering. The Planck scale effects can also change $theta_{12}$ up to a few degrees in either direction for quasi-degenerate neutrinos. These effects may dominate over the RG effects in the SM, and in the MSSM with small $tan beta$. The usual constraints on neutrino masses, Majorana phases or $tan beta$ stemming from RG running arguments can then be relaxed. We quantify the extent of Planck effects on the mixing angles in terms of mismatch phases which break the symmetries leading to TBM. In particular, we show that when the mismatch phases vanish, the mixing angles are not affected in spite of the Planck scale contribution. Similar statements may be made for $mu$-$tau$ symmetric mass matrices.
We scrutinize corrections to tribimaximal (TBM), bimaximal (BM) and democratic (DC) mixing matrices for explaining recent global fit neutrino mixing data. These corrections are parameterized in terms of small orthogonal rotations (R) with corresponding modified PMNS matrices of the forms big($R_{ij}^lcdot U,~Ucdot R_{ij}^r,~U cdot R_{ij}^r cdot R_{kl}^r,~R_{ij}^l cdot R_{kl}^l cdot U$big ) where $R_{ij}^{l, r}$ is rotation in ij sector and U is any one of these special matrices. We showed that for perturbative schemes dictated by single rotation, only big($ R_{12}^lcdot U_{BM},~R_{13}^lcdot U_{BM},~U_{TBM}cdot R_{13}^r$ big ) can fit the mixing data at $3sigma$ level. However for $R_{ij}^lcdot R_{kl}^lcdot U$ type rotations, only big ($R_{23}^lcdot R_{13}^l cdot U_{DC} $big ) is successful to fit all neutrino mixing angles within $1sigma$ range. For $Ucdot R_{ij}^rcdot R_{kl}^r$ perturbative scheme, only big($U_{BM} cdot R_{12}^rcdot R_{13}^r$,~$U_{DC} cdot R_{12}^rcdot R_{23}^r$,~$U_{TBM} cdot R_{12}^rcdot R_{13}^r$big ) are consistent at $1sigma$ level. The remaining double rotation cases are either excluded at 3$sigma$ level or successful in producing mixing angles only at $2sigma-3sigma$ level. We also updated our previous analysis on PMNS matrices of the form big($R_{ij}cdot U cdot R_{kl}$big ) with recent mixing data. We showed that the results modifies substantially with fitting accuracy level decreases for all of the permitted cases except big($R_{12}cdot U_{BM}cdot R_{13}$, $R_{23}cdot U_{TBM}cdot R_{13}$ and $R_{13}cdot U_{TBM} cdot R_{13}$big ) in this rotation scheme.
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