Search for ZZ and Zγ^* production in p-barp collisions at sqrt(s) = 1.96 TeV and limits on anomalous ZZZ and ZZγ^* couplings

Abstract

We present a study of four muon, four electron, and two muon two electron events using 1 fb^(-1) of data collected with the D0 detector at the Fermilab Tevatron p-barp Collider at sqrt(s) = 1.96 TeV. Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13 +- 0.03 events and with the predicted standard model ZZ and Zγ^* production of 1.71 +-0.15 events. We set an upper limit on the ZZ and Zγ^* cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZγ^* gauge couplings. The one-parameter 95%$ C.L. coupling limits with a form factor scale Lambda = 1.2 TeV are -0.28 < f_(40)^Z < 0.28, -0.31 < f_(50)^Z < 0.29, -0.26 < f_(40)^γ< 0.26, and -0.30 < f_(5 0)^γ< 0.28.

Figures (1)

• Figure 1: Limits on anomalous couplings for $\Lambda = 1.2$ TeV: (a) $f_{40}^{\gamma}$ vs. $f_{40}^Z$, (b) $f_{40}^{\gamma}$ vs. $f_{50}^{\gamma}$, (c) $f_{40}^Z$ vs. $f_{50}^Z$, and (d) $f_{50}^{\gamma}$ vs. $f_{50}^Z$, assuming in each case that the other two couplings are zero. The inner and outer curves are the $95 \%$ C.L. two-degree of freedom exclusion contour and the constraint from the unitarity condition, respectively. The inner crosshairs are the $95 \%$ C.L. one-degree of freedom exclusion limits.