Process-independent radiative corrections in the minimal supersymmetric standard model.

Abstract

We systematically study supersymmetric corrections to the two-point functions of the electroweak gauge bosons. These corrections are process independent in the sense that they affect all electroweak gauge interactions. We present our results for three relevant physical quantities: the $\ensuremath{\rho}$ parameter, the mass of the $W$ boson, and the effective parameter ${sin}^{2}{\stackrel{^}{\ensuremath{\theta}}}_{W}(1+\ensuremath{\delta}\stackrel{^}{\ensuremath{\kappa}})$ that measures the strength of vector couplings of the $Z$. We find that in models with general softly broken supersymmetry corrections due to supersymmetric particles can be quite sizable; they can compensate a decrease of ${m}_{t}$ of 60 GeV. Because of dynamical threshold enhancement, their effect on ${m}_{W}$ and ${sin}^{2}{\stackrel{^}{\ensuremath{\theta}}}_{W}(1+\ensuremath{\delta}\stackrel{^}{\ensuremath{\kappa}})$ can be even bigger if some sparticle mass is close to $\frac{{m}_{Z}}{2}$. We also study correlations between the three observables; these correlations are very strong in the standard model, but can be substantially weaker in supersymmetric models if some sparticle masses lie below 80-100 GeV. Finally, we discuss supergravity models with radiative gauge symmetry breaking; we find that the maximal corrections in these models are reduced by roughly 40-50% compared to the case of general softly broken supersymmetry.