ANALYTICAL EXPRESSIONS FOR RADIATIVELY CORRECTED HIGGS MASSES AND COUPLINGS IN THE MSSM

We propose, for the computation of the Higgs mass spectrum and couplings, a renormalization-group improved leading-log approximation, where the renormalization scale is fixed to the top-quark pole mass. For the case m(A) similar to M(SUSY), our leading-log approximation differs by less than 2 GeV from previous results on the Higgs mass computed using a nearly scale independent renormalization-group improved effective potential up to next-to-leading order. Moreover, for the general case m(A) less than or similar to M(SUSY), we provide analytical formulae (including two-loop leading-log corrections) for all the masses and couplings in the Higgs sector. For M(SUSY) less than or similar to 1.5 TeV and arbitrary values of m(A), tan beta and the stop mixing parameters, they reproduce the numerical renormalization-group improved leading-log result for the Higgs masses with an error of less than 3 GeV. For the Higgs couplings, our analytical formulae reproduce the numerical results equally well. Comparison with other methods is also performed.