Improved Higgs mass stability bound in the standard model and implications for supersymmetry

We re-examine the lower bound on the mass of the Higgs boson, Mh, from Standard Model vaccum stability including next-to-leading-log radiative corrections. This amounts to work with the full one-loop effective potential, V(θ), improved by two-loop RGE, and allows to keep control of the scale invariance of V in a wide range of the θ-field. Our results show that the bound is O (10 GeV) less stringent than in previous estimates. In addition we perform a detailed comparison between the SM lower bounds on Mh and the supersymmetric upper bounds on it. It turns out that depending on the actual value of the top mass, Mt, the eventually measured Higgs mass can discard the pure SM, the Minimal Supersymmetric Standard Model or both.