Thursday, March 15, 2012

1203.2646 (G. C. Branco et al.)

Spontaneous leptonic CP violation and nonzero $θ_{13}$    [PDF]

G. C. Branco, R. Gonzalez Felipe, F. R. Joaquim, H. Serodio
We consider a simple extension of the Standard Model by adding two Higgs triplets and a complex scalar singlet to its particle content. In this framework, the CP symmetry is spontaneously broken at high energies by the complex vacuum expectation value of the scalar singlet. Such a breaking leads to leptonic CP violation at low energies. The model also exhibits an $A_4\times Z_4$ flavour symmetry which, after being spontaneously broken at a high-energy scale, yields a tribimaximal pattern in the lepton sector. We consider small perturbations around the tribimaximal vacuum alignment condition in order to generate nonzero values of $\theta_{13}$, as required by the latest neutrino oscillation data. It is shown that the value of $\theta_{13}$ recently measured by the Daya Bay Reactor Neutrino Experiment can be accommodated in our framework together with large Dirac-type CP violation. We also address the viability of leptogenesis in our model through the out-of-equilibrium decays of the Higgs triplets. In particular, the CP asymmetries in the triplet decays into two leptons are computed and it is shown that the effective leptogenesis and low-energy CP-violating phases are directly linked.
View original: http://arxiv.org/abs/1203.2646

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