E6 models from F-theory

Abstract

F-theory is a non-perturbative formulation of type IIB superstring theory which allows for the decoupling of gravity and for the formulation of GUT theories based on the gauge group E 6. In this paper we explore F-theory models in which the low energy supersymmetric theory contains the particle content of three 27 dimensional representations of the underlying E 6 gauge group, plus two extra right-handed neutrinos predicted from F and D flatness. The resulting TeV scale effective theory resembles either the E6SSM or the NMSSM+, depending on whether an additional Abelian gauge group does or does not survive. However there are novel features compared to both these models as follows: (i) If the additional Abelian gauge group is unbroken then it can have a weaker gauge coupling than in the E6SSM; (ii) If the additional Abelian gauge group is broken then non-perturbative effects can violate the scale invariance of the NMSSM+ leading to a generalised model; (iii) Unification is achieved not at the field theory level but at the F-theory level since the gauge couplings are split by flux effects, negating the need for any additional doublet states which are usually required; (iv) Proton decay is suppressed by the geometric coupling suppression of a singlet state, a mechanism peculiar to F-theory, which effectively suppresses the coupling of the exotic charge −1/3 colour triplet state D to quarks and leptons; (v) The $ \overline{D} $ decays as a chiral leptoquark with couplings to left-handed quarks and leptons, providing characteristic and striking signatures at the LHC.