Would a Light Higgs Detection Imply New Physics?

Abstract

Depending on the Higgs-boson and top-quark masses, $M_H$ and $M_t$, the effective potential of the Standard Model can develop a non-standard minimum for values of the field much larger than the weak scale. In those cases the standard minimum becomes metastable and the possibility of decay to the non-standard one arises. Comparison of the decay rate to the non-standard minimum at finite (and zero) temperature with the corresponding expansion rate of the Universe allows to identify the region, in the ($M_H$, $M_t$) plane, where the Higgs field is sitting at the standard electroweak minimum. Since that region depends on the cutoff scale $Λ$, up to which we believe the Standard Model, the discovery of the Higgs boson, mainly at LEP-200, might put an upper bound (below the Planck scale) on the scale of new physics $Λ$.