Limit on the rare decay B → μ+μ- K±

We report on a search for flavor-changing neutral current decays of B mesons into μμK± using data obtained in the Collider Detector at Fermilab (CDF) 1992--1993 data taking run. To reduce the amount of background in our data we use precise tracking information from the CDF silicon vertex detector to pinpoint the location of the decay vertex of the B candidate, and accept only events which have a large decay time. We compare this data to a B meson signal obtained in a similar fashion, but where the muon pears originate from ψ decays, and calculate the relative branching ratios. In absence of any indication of flavor-changing neutral current decay we set an upper limit on the branching ratio of 3.2 x 10-1, which is consistent with Standard Model expectations but leaves little room for non-standard physics