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

We propose, for the computation of the Higgs mass spectrum and couplin gs, 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 b y less than 2 GeV from previous results on the Higgs mass computed usi ng 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 co uplings in the Higgs sector. For M(SUSY) less than or similar to 1.5 T eV and arbitrary values of m(A), tan beta and the stop mixing paramete rs, they reproduce the numerical renormalization-group improved leadin g-log result for the Higgs masses with an error of less than 3 GeV. Fo r the Higgs couplings, our analytical formulae reproduce the numerical results equally well. Comparison with other methods is also performed .