Evidence of WW and WZ production with lepton + jets final states in pp collisions at square root s=1.96 TeV.

We present first evidence for WW+WZ production in lepton+jets final states at a hadron collider. The data correspond to 1.07 fb{sup -1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron in pp collisions at {radical}(s)=1.96 TeV. The observed cross section for WW+WZ production is 20.2{+-}4.5 pb, consistent with the standard model and more precise than previous measurements in fully leptonic final states. The probability that background fluctuations alone produce this excess is <5.4x10{sup -6}, which corresponds to a significance of 4.4 standard deviations.