The Mass of the Lightest Supersymmetric Higgs Boson beyond the Leading Logarithm Approximation

We examine the radiative corrections to the mass of the lightest Higgs boson in the minimal supersymmetric extension of the standard model. We use the renormalization-group improved effective potential which includes the next-to-leading-order contributions. We find that, contrary to the result of Espinosa and Quir'os, the higher-order corrections to the lightest Higgs boson mass are non-negligible, adding $3-11$ GeV ($3-9$ GeV) to the result in the leading logarithm approximation for the range of top quark mass $100 {\rm GeV} < m_t < 200 {\rm GeV}$andforthesupersymmetricbreakingscale$M_{\rm SUSY} = 1 {\rm TeV}$($M_{\rm SUSY} = 10 {\rm TeV}$). Also we find that our result is stable under the change of the renormalization parameter $t$.