Measurement of the ratio of the pp¯→W+c-jet cross section to the inclusive pp¯→W+jets cross section

We present a measurement of the fraction of inclusive W+jetsW+jets events produced with net charm quantum number ±1, denoted W+cW+c-jet, in pp¯ collisions at s=1.96 TeV using approximately 1 fb−1 of data collected by the DØ detector at the Fermilab Tevatron Collider. We identify the W+jetsW+jets events via the leptonic W   boson decays. Candidate W+cW+c-jet events are selected by requiring a jet containing a muon in association with a reconstructed W boson and exploiting the charge correlation between this muon and W   boson decay lepton to perform a nearly model-independent background subtraction. We measure the fraction of W+cW+c-jet events in the inclusive W+jetsW+jets sample for jet pT>20 GeVpT>20 GeV and pseudorapidity |η|<2.5|η|<2.5 to be 0.074±0.019(stat.)±0.0140.012(syst.), in agreement with theoretical predictions. The probability that background fluctuations could produce the observed fraction of W+cW+c-jet events is estimated to be 2.5×10−42.5×10−4, which corresponds to a 3.5σ statistical significance.