General Lepton Mixing in Holographic Composite Higgs Models

Abstract

We introduce a scenario of lepton mixing in holographic composite Higgs models based on non-abelian discrete symmetries of the form G_f=X x Z_N, broken to Z_2 x Z_2 x Z_N in the elementary sector and to Z_N^(D) in the composite sector with Z_N^(D) being the diagonal subgroup of a Z_N contained in X and the external Z_N. By choosing X = Delta(96) or Delta(384), a non-vanishing theta_{13} of order 0.1 is naturally obtained. We apply our considerations to a 5D model in warped space for the particular cases of X = S_4, A_5, Delta(96) and Delta(384) and N=3 or 5. Lepton flavour violating processes and electric dipole moments are well below the current bounds, with the exception of mu -> e gamma that puts a very mild constraint on the parameter space of the model, for all presented choices of G_f.

20 pages, 2 figures; v2: clarifications added in section 2 regarding the form of the flavour group and the size of the flavour violating kinetic terms, typos corrected, minor improvements, to appear in JHEP