1205.1051 (Stefan Antusch et al.)

θ^{PMNS}_{13} = θ_C / \sqrt{2} from GUTs    [PDF]

Stefan Antusch, Christian Gross, Vinzenz Maurer, Constantin Sluka

The recent observations of the leptonic mixing angle \theta^{PMNS}_{13} are consistent with \theta^{PMNS}_{13} = \theta_C / \sqrt{2} (with \theta_C being the Cabibbo angle \theta^{CKM}_{12}). We discuss how this relation can emerge in Grand Unified Theories via charged lepton corrections. The key ingredient is that in GUTs the down-type quark Yukawa matrix as well as the charged lepton Yukawa matrix are generated from the same set of GUT operators, which implies that the resulting entries are linked and may differ only by group theoretical Clebsch factors. This allows a link \theta^e_{12} = \theta_C to be established, which can induce \theta^{PMNS}_{13} = \theta_C / \sqrt{2} provided that the 1-3 mixing in the neutrino mass matrix is much smaller than \theta_C. We find simple conditions under which \theta^{PMNS}_{13} = \theta_C / \sqrt{2} can arise via this link in SU(5) GUTs and Pati-Salam models. Including mixing patterns for the neutrino sector, explicit scenarios can be distinguished by their different predictions for the Dirac CP phase \delta^{PMNS}.

View original: http://arxiv.org/abs/1205.1051