Abstract
We study low energy implications of F-theory GUT models based on SU(5) extended by a U(1)' symmetry which couples non-universally to the three families of quarks and leptons. This gauge group arises naturally from the maximal exceptional gauge symmetry of an elliptically fibred internal space, at a single point of enhancement, E_8supset SU(5)times SU(5)'supset SU(5)times U(1)^4. Rank-one fermion mass textures and a tree-level top quark coupling are guaranteed by imposing a Z_2 monodromy group which identifies two abelian factors of the above breaking sequence. The U(1)' factor of the gauge symmetry is an anomaly free linear combination of the three remaining abelian symmetries left over by Z_2. Several classes of models are obtained, distinguished with respect to the U(1)' charges of the representations, and possible extra zero modes coming in vector-like representations. The predictions of these models are investigated and are compared with the LHC results and other related experiments. Particular cases interpreting the B-meson anomalies observed in LHCb and BaBar experiments are also discussed.
Highlights
In the present work we have examined the low energy implications of F-theory SU (5) × U (1) grand unified theories (GUTs) models embedded in SU (5) × SU (5) ⊃ SU (5) × U (1)4
This gauge symmetry emerges naturally from a single point of E8 enhancement, associated with the maximal geometric singularity appearing in the elliptic fibration of the internal manifold
In order to ensure realistic fermion mass textures and a tree-level top quark Yukawa coupling, we have imposed a Z2 monodromy group which acts on the geometric configuration of 7-branes and identifies two out of the four abelian factors descending from the SU (5) reduction
Summary
We first consider the neutral part of the Lagrangian including the Z interactions with fermions in the gauge eigenstates basis [23,24]: Page 3 of 28 35. Where f ( f R0) is a column vector of left (right) chiral fermions of a given type (u, d, e or ν) in the gauge basis and q fL,R are diagonal 3 × 3 matrices of U (1) charges. FL denotes chiral fermions in the mass eigenstates basis, related to gauge eigenstates via unitary transformations of the form f. The neutral current (2.2) takes the form:. For models with family non-universal U (1) charges, the mixing matrix Q fL is non-diagonal and flavour violating terms appear in the effective theory
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