Study of the High-Mass Dimuon Continuum in 400-GeV Proton-Nucleus Collisions

The mass spectrum of muon pairs in the range 5 to 15 GeV is studied in the inclusive reaction $p+\mathrm{nucleus}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}+{\ensuremath{\mu}}^{\ensuremath{-}}+\mathrm{anything}$. The $\ensuremath{\Upsilon}$ and continuum distribution are presented as is the $A$ dependence of the continuum. Comparison with a parton-annihilation model yields a sea-quark distribution.