Abhijit Borah
Articles written in Pramana – Journal of Physics
Volume 69 Issue 4 October 2007 pp 533-549 Research Articles
N Nimai Singh Monisa Rajkhowa Abhijit Borah
We explore a novel possibility for lowering the solar mixing angle ($\theta_{12}$) from tri-bimaximal mixings, without sacriﬁcing the predictions of maximal atmospheric mixing angle ($\theta_{23} = 45^{\circ}$) and zero reactor angle ($\theta_{13} = 0^{\circ}$) in the inverted and normal hierarchical neutrino mass models having 2-3 symmetry. This can be done through the identiﬁcation of a ﬂavour twister term in the texture of neutrino mass matrix and the variation of such term leads to lowering of solar mixing angle. For the observed ranges of $\Delta m_{21}^{2}$ and $\Delta m_{23}^{2}$, we calculate the predictions on tan^{2} $\theta_{12} = 0.5, 0.45, 0.35$ for different input values of the parameters in the neutrino mass matrix. We also observe a possible transition from inverted hierarchical model having even CP parity (Type-IHA) to inverted hierarchical model having odd CP parity (Type-IHB) in the ﬁrst two mass eigenvalues, when there is a change in input values of parameters in the same mass matrix. The present work differs from the conventional approaches for the deviations from tri-bimaximal mixing, where the 2-3 symmetry is broken, leading to $\theta_{23} \neq 45^{\circ}$ and $\theta_{13} \neq 0^{\circ}$.
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