The lightest Higgs boson mass in the Minimal Supersymmetric Standard Model Original Research Article

We compute the upper bound on the mass of the lightest Higgs boson in the Minimal Supersymmetric Standard Model in a model-independent way, including leading (one-loop) and next-to-leading order (two-loop) radiative corrections. We find that (contrary to some recent claims) the two-loop corrections are negative with respect to the one-loop result and relatively small (⪅ 3%). After defining physical (pole) top quark mass Mt, by including QCD self-energies, and physical Higgs mass MH, by including the electroweak self-energies ∏ (MH2) − ∏ (0), we obtain the upper limit on MH as a function of supersymmetric parameters. We include as supersymmetric parameters the scale of supersymmetry breaking Ms, the value of tan β and the mixing between stops Xt = At + μ cot β (which is responsible for the threshold correction on the Higgs quartic coupling). Our results do not depend on further details of the supersymmetric model. In particular, for Ms ⩽ 1 TeV, maximal threshold effect Xt2 = 6MS2 and any value of tan β, we find MH ⩽ 140 GeV for Mt ⩽ 190 GeV. In the particular scenario where the top is in its infrared fixed point we find MH ⩽ 86 GeV for Mt = 170 GeV.