First Observation of Vector Boson Pairs in a Hadronic Final State at the Tevatron Collider

We present the first observation in hadronic collisions of the electroweak production of vector boson pairs ($VV$, $V=W$, $Z$) where one boson decays to a dijet final state. The data correspond to $3.5{\mathrm{fb}}^{-1}$ of integrated luminosity of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected by the CDF II detector at the Fermilab Tevatron. We observe $1516\pm 239(\mathrm{stat})\pm 144(\mathrm{syst})$ diboson candidate events and measure a cross section $\sigma (p\overline{p}\to VV+X)$ of $18.0\pm 2.8(\mathrm{stat})\pm 2.4(\mathrm{syst})\pm 1.1(\mathrm{lumi})\mathrm{pb}$, in agreement with the expectations of the standard model.

Figure 1

Data compared with the sum of the predicted EWK and MJB backgrounds for the $\Delta {\varphi }_{{\mathrm{E̸}}_T}^{\mathrm{jet}}$ variable. The band represents the total systematic uncertainty on the background. The measured signal is included here in the EWK contribution.

Figure 2

Top: Comparison between data and fitted background only. The measured signal is shown unstacked. The band represents the systematic uncertainty due to the shape of EWK background as described in the text. Bottom: Comparison of the diboson signal (solid line) with the background-subtracted data (points). The dashed lines represent the $\pm 1\sigma$ statistical variations on the extracted signal. The gray band represents the systematic uncertainty due to the EWK shape.