Supersymmetric heavy Higgs bosons at e+e- linear collider and dark-matter physics

We consider the capability of the e+e- linear collider (which has recently been called the International Linear Collider, or ILC) for studying the properties of the heavy Higgs bosons in the supersymmetric standard model. We pay special attention to the large tan β region which is motivated, in particular, by explaining the dark-matter density of the universe (i.e., so-called "rapid-annihilation funnels"). We perform a systematic analysis to estimate expected uncertainties in the masses and widths of the heavy Higgs bosons assuming an energy and integrated luminosity of s=1TeV and L=1ab-1. We also discuss its implication to the reconstruction of the dark-matter density of the universe.