Charged Lepton Corrections Research Articles

Different Mixing Scenerio of Quasi-Degenerate Neutrino with Charged Lepton Correction

Theoretically, in order to achieve non-zero θ13 a little deviation from Tribimaximal Mixing (TBM) pattern is needed, especially on θ13 without perturbing the atmospheric and solar mixing angles. In this work we computed the neutrino mixing angles by disturbing the θ13 as well as θ12 in Bimaximal (BM) and Hexagonal mixing (HM) using non-diagonal charged lepton mass. Considering the standard form of mass texture which satisfies TBM we have shown the quasi-degenerate nature of neutrino. This quasi degenerate type of mass matrix for BM and HM is then used to calculate the deviated mixing pattern which are consistent with recent neutrino oscillation data.

Large neutrino mixing angleθ13MNSand quark-lepton mass ratios in unified flavor models

We analyse how a large value of the leptonic mixing angle \theta_{13}^{MNS} can be generated via charged lepton corrections in unified flavour models, using novel combinations of Clebsch-Gordan factors for obtaining viable quark-lepton mass ratios for the first two families. We discuss how these Clebsch-Gordan factors affect the relations between down-type quark mixing and charged lepton mixing in SU(5) GUTs and Pati-Salam unified models and calculate the resulting possible predictions for \theta_{13}^{MNS} for models with \theta_{13}^\nu, \theta_{13}^e << \theta_{12}^e. While symmetric mass matrices with zero (1,1)-elements always lead to comparatively small \theta_{13}^{MNS} \approx 2.8 degrees, we find novel combinations of Clebsch-Gordan factors for non-symmetric mass matrices which can yield \theta_{13}^{MNS} \approx 5.1 degrees, 6.1 degrees, 7.6 degrees or 10.1 degrees, as favoured by the current experimental hints for large \theta_{13}^{MNS}. We discuss applications to classes of models with underlying tri-bimaximal or bimaximal mixing in the neutrino sector.

Parametrizing the lepton mixing matrix in terms of charged lepton corrections

We consider a parametrization of the lepton mixing matrix in which the deviations from maximal atmospheric mixing and vanishing reactor mixing are obtained in terms of small corrections from the charged lepton sector. Relatively large deviations for the reactor mixing angle from zero as indicated by T2K experiment can be obtained in this parametrization. We are able to further reduce the number of complex phases, thus, simplifying the analysis. In addition, we have obtained the sides of unitarity triangles and the vacuum oscillation probabilities in this parametrization. The Jarlskog rephasing invariant measure of CP violation at the leading order has a single phase difference which can be identified as Dirac-type CP violating phase in this parametrization.

Large|Ue3|and tribimaximal mixing

We investigate in a model-independent way to what extent one can perturb tribimaximal mixing in order to generate a sizable value of $|{U}_{e3}|$, while at the same time keeping solar neutrino mixing near its measured value, which is close to ${sin}^{2}{\ensuremath{\theta}}_{12}=\frac{1}{3}$. Three straightforward breaking mechanisms to generate $|{U}_{e3}|\ensuremath{\simeq}0.1$ are considered. For charged lepton corrections, the suppression of a sizable contribution to ${sin}^{2}{\ensuremath{\theta}}_{12}$ can be achieved if $CP$ violation in neutrino oscillations is almost maximal. Generation of the indicated value of $|{U}_{e3}|\ensuremath{\simeq}0.1$ through renormalization group corrections requires the neutrinos to be quasidegenerate in mass. The consistency with the allowed range of ${sin}^{2}{\ensuremath{\theta}}_{12}$ together with large running of $|{U}_{e3}|$ forces one of the Majorana phases to be close to $\ensuremath{\pi}$. This implies large cancellations in the effective Majorana mass governing neutrinoless double beta ($(\ensuremath{\beta}\ensuremath{\beta}{)}_{0\ensuremath{\nu}}$) decay, constraining it to lie near its minimum allowed value of ${m}_{0}\mathrm{cos}2{\ensuremath{\theta}}_{12}$, where ${m}_{0}\ensuremath{\gtrsim}0.1\text{ }\text{ }\mathrm{eV}$. Finally, explicit breaking of the neutrino mass matrix in the inverted hierarchical and quasidegenerate neutrino mass spectrum cases is similarly correlated with the $(\ensuremath{\beta}\ensuremath{\beta}{)}_{0\ensuremath{\nu}}$-decay effective Majorana mass, although to a lesser extent. The implied values for the atmospheric neutrino mixing angle ${\ensuremath{\theta}}_{23}$ are given in all cases.

Perturbative estimates of lepton mixing angles in unified models

Many unified models predict two large neutrino mixing angles, with the charged lepton mixing angles being small and quark-like, and the neutrino masses being hierarchical. Assuming this, we present simple approximate analytic formulae giving the lepton mixing angles in terms of the underlying high energy neutrino mixing angles together with small perturbations due to both charged lepton corrections and renormalisation group (RG) effects, including also the effects of third family canonical normalization (CN). We apply the perturbative formulae to the ubiquitous case of tri-bimaximal neutrino mixing at the unification scale, in order to predict the theoretical corrections to mixing angle predictions and sum rule relations, and give a general discussion of all limiting cases. We also discuss the implications for the sum rule relations of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.

Deviations from tri-bimaximal mixing

Current data indicates that lepton mixing is very close to the tri-bimaximal mixing scenario. In general, however, one expects deviations from any mixing scenario. We discuss several examples to perturb tri-bimaximal mixing, namely soft breaking, renormalization group running and charged lepton corrections. We also present a convenient parametrization of the PMNS matrix which takes advantage of the apparently close to tri-bimaximal mixing pattern. Finally, it is discussed how to generate values of U_{e3} which correspond to the recently found hint for non-zero U_{e3}.

Deviations from tribimaximal mixing: Charged lepton corrections and renormalization group running

We analyze the effects of charged lepton corrections and renormalization group (RG) running on the low energy predictions of theories which accurately predict tri-bimaximal neutrino mixing at the high energy scale. In particular we focus on grand unified theory (GUT) inspired seesaw models with accurate tri-bimaximal neutrino mixing at the GUT scale, in which the charged lepton corrections are Cabibbo-like and give rise to sum rules valid at the GUT scale. We study numerically the RG corrections to a variety of such neutrino mixing sum rules in order to assess their accuracy and reliability when comparing them to future low energy neutrino oscillation experiments. Our results indicate that the RG corrections to neutrino mixing sum rules are typically small (less than one degree), at least in the examples studied with hierarchical neutrinos.

Lepton flavour violation in the constrained MSSM with constrained sequential dominance

We consider charged lepton flavour violation (LFV) in the constrained minimal supersymmetric Standard Model, extended to include the see-saw mechanism with constrained sequential dominance (CSD), where CSD provides a natural see-saw explanation of tri-bimaximal neutrino mixing. When charged lepton corrections to tri-bimaximal neutrino mixing are included, we discover characteristic correlations among the LFV branching ratios, depending on the mass ordering of the right-handed neutrinos, with a pronounced dependence on the leptonic mixing angle θ13 (and in some cases also on the Dirac CP phase δ).

Neutrino mixing sum rules and oscillation experiments

The neutrino mixing sum rule $\theta_{12} - \theta_{13}\cos(\delta) \approx \theta^\nu_{12}$ provides a possibility to explore the structure of the neutrino mass matrix in the presence of charged lepton corrections, since it relates the 1-2 mixing angle from the neutrino mass matrix, $\theta_{12}^\nu$, to observable parameters of the PMNS mixing matrix. The neutrino mixing sum rule holds if the charged lepton mixing angles are CKM-like, i.e., small and dominated by a 1-2 mixing, and for small 1-3 mixing in the neutrino mass matrix. These conditions hold in a wide class of well motivated flavour models. We apply this sum rule to present oscillation data, and we investigate the prospects of future neutrino facilities for exploring the sum rule by simulating various setups for long-baseline reactor and accelerator experiments. As explicit examples, we use the sum rule to test the hypotheses of tri-bimaximal and bimaximal neutrino mixing, where $\theta^\nu_{12}$ is predicted by $\sin^2(\theta^\nu_{12}) = 1/3$ or 1/2, respectively, although the neutrino mixing sum rule can be used to test any prediction for $\theta^\nu_{12}$.

Lowering solar mixing angle in inverted hierarchy without charged lepton corrections

In the present work, the inverted hierarchical neutrino mass model which is characterized by opposite CP parity in the first two mass eigenvalues (m1, − m2, m3), is studied in order to lower the predicted value of the solar mixing angle tan2θ12, from the tri-bimaximal mixing (TBM), without sacrificing the conditions of maximal atmospheric mixing angle (θ23 = π/4) and zero reactor angle (θ13 = 0). The present attempt is different from the earlier approach where the correction from the charged lepton mass matrix is included in the leptonic mixing matrix to lower the prediction on solar mixing angle. The lowering of the solar mixing angle without charged lepton correction can be obtained through the variation of the input value of a flavour twister term present in the texture of neutrino mass matrix having a 2-3 symmetry. The present analysis agrees with the latest experimental bounds on ▵m221 and |▵m223|. It also represents an important result on the survival of the inverted hierarchical neutrino mass models having opposite CP parity in the first two eigenvalues.

Charged lepton corrections to neutrino mixing angles and CP phases revisited

We re-analyze charged lepton corrections to neutrino mixing angles and CP phases, carefully including CP phases from the charged lepton sector. We present simple analytical formulae for including the charged lepton corrections and derive compact new results for small neutrino and charged lepton mixings θ 13 ν and θ 13 e . We find a generic relation θ 12 + 1 2 θ 12 e cos ( δ − π ) ≈ θ 12 ν , which relates the prediction from the neutrino sector θ 12 ν to the charged lepton mixing θ 12 e and to the MNS neutrino oscillation phase δ. We apply our formula to the examples of bimaximal or tri-bimaximal neutrino mixing. One implication is that the so-called quark–lepton complementarity relation θ 12 + θ C = 45 ° can only hold for δ = π and it gets modified in the presence of leptonic CP violation. On the other hand, the lepton mixing θ 13 generated from the charged lepton correction θ 12 e is independent of CP phases and given by θ 13 = 1 2 θ 12 e . Combining these results leads to a model-independent sum rule: θ 12 + θ 13 cos ( δ − π ) ≈ θ 12 ν where θ 12 ν = ( 35.26 ° ) 45 ° in the case of (tri-)bimaximal neutrino mixing, for example.