Measurement of WW + WZ production cross section and study of the dijet mass spectrum in the ℓν + jets final state at CDF

Abstract

We present the measurement of the WW and WZ production cross section in p$\bar{p}$ collisions at √s = 1.96 TeV, in a final state consisting of an electron or muon, neutrino and jets. The data analyzed were collected by the CDF II detector at the Tevatron collider and correspond to 4.3 fb-1 of integrated luminosity. The analysis uses a fit to the dijet mass distribution to extract the diboson contribution. We observe 1582 ± 275(stat.) ± 107(syst.) diboson candidate events and measure a cross section of σWW/WZ = 18.1 ± 3.3(stat.) ± 2.5(syst.) pb, consistent with the Standard Model prediction of 15.9 ± 0.9 pb. The best fit to the dijet mass of the known components shows a good agreement with the data except for the [120, 160] GeV/c2 mass range, where an excess is observed. We perform detailed checks of our background model and study the significance of the excess, assuming an additional gaussian component with a width compatible with the expected dijet mass resolution. A standard Δχ2 test of the presence of the additional component, returns a p-value of 4.2 x 10-4 when standard sources of systematics are considered, corresponding to a significance of 3.3{sigma}.