Eur. Phys. J. C (2011) 71: 1768
https://doi.org/10.1140/epjc/s10052-011-1768-1

Regular Article - Theoretical Physics

Unification, KK-thresholds and the top Yukawa coupling in F-theory GUTs

¹ Theoretical Physics Division, Ioannina University, 45110, Ioannina, Greece
² Physics Department, National Technical University, 157 73, Athens, Greece

^* e-mail: ntrac@central.ntua.gr

Received: 9 July 2011
Revised: 5 September 2011
Published online: 1 October 2011

Abstract

In a class of F-theory SU(5) GUTs the low energy chiral mass spectrum is obtained from rank one fermion mass textures with a hierarchical structure organized by U(1) symmetries embedded in the exceptional E ₈ group. In these theories chiral fields reside on matter ‘curves’ and the tree-level masses are computed from integrals of overlapping wave functions of the particles at the triple intersection points. This calculation requires knowledge of the exact form of the wave functions. In this work we propose a way to obtain a reliable estimate of the various quantities which determine the strength of the Yukawa couplings. We use previous analysis of KK-threshold effects to determine the (ratios of) heavy mass scales of the theory which are involved in the normalization of the wave functions. We consider similar effects from the chiral spectrum of these models and discuss possible constraints on the emerging matter content. In this approach, we find that the Yukawa couplings can be determined solely from the U(1) charges of the states in the ‘intersection’ and the torsion which is a topological invariant quantity. We apply the results to a viable SU(5) model with minimal spectrum which satisfies all the constraints imposed by our analysis. We use renormalization group analysis to estimate the top and bottom masses and find that they are in agreement with the experimental values.