Coupling Sum Rules and Oblique Corrections in Gauge-Higgs Unification

TL;DR

This paper investigates gauge-Higgs unification models in warped spacetime, revealing sum rules that ensure finite corrections to electroweak parameters and showing that fermion loop corrections are minimal.

Contribution

It introduces specific sum rules in GHU models that guarantee finiteness of certain corrections and proposes improved oblique parameters based on these sum rules.

Findings

Sum rules among coupling matrices are numerically confirmed with high accuracy.

Oblique corrections from fermion loops are small in these models.

Sum rules ensure finiteness of vacuum polarization corrections.

Abstract

In GUT inspired $SO(5) \times U(1)_X \times SU(3)_C$ gauge-Higgs unification (GHU) in the Randall-Sundrum warped spacetime, the $W$ and $Z$ couplings of all 4D fermion modes become nontrivial. The $W$ and $Z$ couplings of zero-mode quarks and leptons slightly deviate from those in the SM, and the couplings take the matrix form in the space of Kaluza-Klein (KK) states. In particular, the 4D couplings and mass spectra in the KK states depend on the Aharonov-Bohm phase $ \theta_H$ in the fifth dimension. Nevertheless there emerge three astonishing sum rules among those coupling matrices, which guarantees the finiteness of certain combinations of corrections to vacuum polarization tensors. We confirm by numerical evaluation that the equality in the sum rules holds with 5 to 7 digits accuracy. Based on the sum rules we propose improved oblique parameters in GHU. Oblique corrections due to fermion 1-loop diagrams are found to be small.