Measurement of the top quark mass using the invariant mass of lepton pairs in soft muon b-tagged events

Abstract

We present the first measurement of the mass of the top quark in a sample of tt̅ →ℓν̅ bb̅ qq̅ events (where ℓ=e,μ) selected by identifying jets containing a muon candidate from the semileptonic decay of heavy-flavor hadrons (soft muon b tagging). The pp̅ collision data used correspond to an integrated luminosity of 2 fb-1 and were collected by the CDF II detector at the Fermilab Tevatron Collider. The measurement is based on a novel technique exploiting the invariant mass of a subset of the decay particles, specifically the lepton from the W boson of the t→Wb decay and the muon from a semileptonic b decay. We fit template histograms, derived from simulation of tt̅ events and a modeling of the background, to the mass distribution observed in the data and measure a top quark mass of 180.5±12.0(stat)±3.6(syst) GeV/c2, consistent with the current world average value.