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Abstract
Presented is a measurement of the simultaneous production of a W± boson in association with a second weak boson (W± or Z 0) in pp¯ collisions at [special characters omitted] = 1.96 TeV. Events are consider with one electron or one muon, missing transverse energy, and at least two hadronic jets. The data were collected by the D0 detector in Run IIa of the Tevatron accelerator and correspond to 1.07 fb−1 of integrated luminosity for each of the two channels (WW/WZ → eνqq¯ and WW/WZ → µνqq¯). The cross section for WW + WZ production is measured to be 20.2 ±2.5(stat) ±3.6(sys) ±1.2(lum) pb with a Gaussian significance of 4.4 standard deviations above the background-only scenario. This measurement is consistent with the Standard Model prediction and represents the first direct evidence for WW and WZ production with semi-leptonic decays at a hadron collider.