Determining tan β from the SUSY Higgs Sector at Future e^+e^- Colliders

We examine the prospects for determining $tan \beta$ from heavy Higgs scalar production in the minimal supersymmetric standard model at a future $e^+ e^-$ collider. Our analysis is independent of assumptions of parameter unification, and we consider general radiative corrections in the Higgs sector. Bounds are presented for $\sqrt{s} = 500$ GeV and 1 TeV, several Higgs masses, a variety of integrated luminosities and b-tagging efficiencies, and in scenarios with and without supersymmetric decays of the Higgs bosons. We find stringent constraints for $3 \alt tan \beta \alt 10$, and, for some scenarios, also interesting bounds on high $tan \beta$ through $tbH^{\pm}$ production. These bounds imply that simple Yukawa unifications may be confirmed or excluded. Implications for soft scalar mass determination and top squark parameters are also discussed.