Standard-model dimuon sources inpp¯collisions

Dimuon events observed at the CERN pp¯ collider offer an opportunity to check the QCD fusion mechanism for heavy-quark production at high $p_T$, along with the Drell-Yan mechanism. We present predicted dimuon rates and distributions from these standard-model sources at √s =630 GeV, for comparison with the forthcoming collider data. The like-sign/unlike-sign dimuon ratio from heavy quarks is sensitive to the details of fragmentation, as well as possible $B^{0\mathrm{-}}$B¯ ${}_{}{}^0{}_{}{}^{}$ mixing. The number of isolated dimuons to be expected from heavy-quark sources is a related question that we discuss. Preliminary data agree well with Drell-Yan predictions for isolated unlike-sign dimuons. For non-isolated dimuons the data lie about a factor 2 below our initial heavy-quark predictions, but this discrepancy is within theoretical uncertainties and can be removed by specific parameter choices. The reported like-sign isolated dimuons cannot be consistently interpreted as heavy-flavor decays without destroying agreement with the Drell-Yan model.