Search for a heavy resonance decaying into a $Z+\mathrm{\text{jet}}$ final state in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using the D0 detector

We have searched for a heavy resonance decaying into a $Z+\mathrm{\text{jet}}$ final state in $p\overline{p}$ collisions at a center of mass energy of $1.96\mathrm{TeV}$ at the Fermilab Tevatron collider using the D0 detector. No indication for such a resonance was found in a data sample corresponding to an integrated luminosity of $370{\mathrm{pb}}^{-1}$. We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production.

Figure 1

The invariant mass of the two selected electrons in the data events.

Figure 2

Invariant mass distribution of the $Z$ boson and the leading jet, $M_{Zj1}$. The data are shown by the full squares with error bars. The actual number of events in a bin is the product of the plotted value and the bin width measured in 10 GeV units. The SM backgrounds generated with pythia are shown in the histograms: $2\to 1$ without threshold (solid line), $2\to 2$ with various $M_{Zq}$ thresholds (discontinuous lines, as indicated). Each curve with a definite $M_{Zq}$ threshold value stops when the curve of the next threshold value takes over. Also shown with open circles is the signal due to an excited quark of 500 GeV mass and narrow width ($\xi =1$). The resonance production cross section is taken from Ref. [1].

Figure 3

$p_{TZ}$ vs $M_{Zj1}$ distributions for a resonance of mass of 500 GeV with $\xi =1$ (dots) and for the SM background (crosses). Both the signal and background events passed through complete reconstruction. Each distribution is arbitrarily normalized.

Figure 4

Upper limit on the resonance cross section times branching fraction at the 95% C.L., ${\sigma }_{95}$, for different resonance masses as a function of the resonance width.

Figure 5

Upper limits on the resonance cross section times branching fraction at the 95% C.L., ${\sigma }_{95}$, for different $\xi$ values as functions of the resonance mass (open symbols). Full circles indicate the LO production cross section of an excited quark times its decay branching fraction into $Z+\mathrm{\text{jet}}$ and $Z\to e^{+}{e}^{-}$, ${\sigma }_{q*}$, for $\xi =1$ [1].