In the Standard Model, divergent radiative corrections destabilize the weak scale with respect to physics at the Planck scale. In extra dimensional models, gauge symmetry itself can be used to protect the Higgs boson. In 5D the potential is fully radiatively generated and breaks the symmetry thanks to the contribution of bulk fermions. Moreover, a flat profile for the vacuum expectation value guarantees the absence of dangerous tree level corrections to precision observables. However, the radiative potential generically prefers a low scale for the new physics, a too light Higgs, and it is hard to accommodate a top heavier than the W boson. We show how to solve these problems in a minimal scenario and without fine tuning in the parameters of the model, at the price of lowering to a marginally acceptable value the scale where the theory becomes strongly coupled. The sole constraint comes from the Zbb coupling, and the experimental bound only requires a few % fine tuning.

Cornell University, USA