$ZZ\to l^{+}{l}^{-}\nu \overline{\nu }$ production in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We describe a search for $Z$ boson pair production in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ with the D0 detector at the Fermilab Tevatron Collider using a data sample corresponding to an integrated luminosity of $2.7{\mathrm{fb}}^{-1}$. Using the final state decay $ZZ\to {\ell }^{+}{\ell }^{-}\nu \overline{\nu }$ (where $\ell =e$ or $\mu$) we find a signal with a 2.6 standard deviations significance (2.0 expected) corresponding to a cross section of $\sigma (p\overline{p}\to ZZ+X)=2.01\pm 0.93(\mathrm{stat})\pm 0.29(\mathrm{sys})\mathrm{pb}$.

Figure 1

Leading order Feynman diagram for the process $ZZ\to {\ell }^{+}{\ell }^{-}\nu \overline{\nu }$.

Figure 2

Representation of the transverse plane of the event and of the decomposition of the dilepton transverse momentum along the thrust axis.

Figure 3

The difference between measured and true dilepton $p_T$ in simulated $Z\to \mu \mu$ events projected along the (a) ${\widehat{a}}_l$ and (b) ${\widehat{a}}_t$ axes.

Figure 4

The ${\mathrm{E̸}}_T^{\prime }$ distributions for dielectron (a) and dimuon (b) events.

Figure 5

The efficiency of $WW$, $WZ$, and $ZZ$ events vs single $Z$ events using the ${\mathrm{E̸}}_T$ (labeled as MET in the figure) and ${\mathrm{E̸}}_T^{\prime }$ variables in the dielectron (a) and dimuon (b) channels.

Figure 6

Distribution in the dielectron channel of the input variables of the likelihood discriminant for data and MC. Invariant mass of the dilepton system (a), $p_T$ of the leading lepton (b), the opening angle between the lead lepton and the dilepton system (c), and the cosine of the scattering angle of the negative lepton in the dilepton rest frame (d).

Figure 7

Distribution in the dimuon channel of the input variables of the likelihood discriminant for data and MC. ${\chi }^2$ probability for the kinematic fit to the dilepton mass (a), $p_T$ of the leading lepton (b), the opening angle between the lead lepton and the dilepton system (c), and the cosine of the scattering angle of the negative lepton in the dilepton rest frame (d).

Figure 8

The likelihood distributions for signal and background: dielectron events (a) and dimuon events (b). All selection requirements have been applied.