On the metastability of the Standard Model vacuum

If the Higgs mass m(H), is as low as suggested by present experimental information, the Standard Model ground state might not be absolutely stable. We present a detailed analysis of the lower bounds on mH imposed by the requirement that the electroweak vacuum be sufficiently long-lived. We perform a complete one-loop calculation of the tunnelling probability at zero temperature, and we improve it by means of two-loop renormalization-group equations. We find that, for m(H) = 115 GeV, the Higgs potential develops an instability below the Planck scale for mt > (166 +/- 2) Gev, but the electroweak vacuum is sufficiently long-lived for m(t) < (175 +/- 2) GeV. (C) 2001 Elsevier Science B.V. All rights reserved.