Two loop effective potential calculation of the lightest CP even Higgs boson mass in the MSSM

Abstract We calculate a two-loop effective potential to the order of O (λ t 2 α s ) in the MSSM. We then study the corresponding two-loop corrections to the CP -even Higgs-boson mass for arbitrary tan β and left-right top-squark mixings. We find that the lightest Higgs-boson mass is changed by at most a few GeV. We also show the improved scale dependence and compare to previous two-loop analyses.