Neutrino masses from an A4 symmetry in holographic composite Higgs models
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Scuola Internazionale Superiore di Studi Avanzati (SISSA)
Neutrino physicsField theories in Higher dimensionsDiscrete and finite symmetries
Águila, F.; Carmona, A.; Santiago, J. Neutrino masses from an A4 symmetry in holographic composite Higgs models. Journal of High Energy Physics, 2010: 127 (2010). [http://hdl.handle.net/10481/30720]
SponsorshipThis work has been partially supported by MICINN project FPA2006-05294, Junta de Andalucía projects FQM 101 and FQM03048. The work of J.S. has been partially supported by SNSF under contract 200021-117873 and by a MICINN Ramón y Cajal contract. The work of A.C. has been supported by a MICINN FPU fellowship.
We show that holographic composite Higgs Models with a discrete A 4 symmetry can be built, which naturally predict hierarchical charged lepton masses and an approximate tri-bimaximal lepton mixing with the correct scale of neutrino masses and a characteristic phenomenology. They also satisfy current constraints from electroweak precision tests, lepton flavor violation and lepton mixing in a large region of parameter space. Two features arise in our model phenomenologically relevant. First, an extra suppression on the lepton Yukawa couplings makes the τ lepton more composite than naively expected from its mass. As a consequence new light leptonic resonances, with masses as low as few hundreds of GeV, large couplings to τ and a very characteristic collider phenomenology, are quite likely. Second, the discrete symmetry A 4 together with the model structure provide a double-layer of flavor protection that allows to keep tree-level mediated processes below present experimental limits. One-loop processes violating lepton flavor, like μ → eγ, may be however observable at future experiments.