Search for a narrow $t\overline{t}$ resonance in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We report a search for a narrow $t\overline{t}$ resonance that decays into a $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ final state based on an integrated luminosity of $5.3{\mathrm{fb}}^{-1}$ of proton-antiproton collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the production cross section of such a resonance multiplied by its branching fraction to $t\overline{t}$. We exclude a leptophobic topcolor $Z^{\prime }$ at the 95% confidence level for masses below 835 GeV (940 GeV) if its width is 1.2% (3%) of its mass. We also exclude color octet vector bosons (colorons) with masses below 775 GeV.

Figure 1

Distributions of $m_{t\overline{t}}$ for resonances with mass $M_X$, normalized to the predicted $\sigma B$ from Table 2.

Figure 2

Distribution of $m_{t\overline{t}}$ for events that pass the final event selection with (a) exactly 3 jets and (b) at least 4 jets, compared with expectations for standard model processes and a 950 GeV resonance signal with the best fitted $\sigma B=0.10\mathrm{pb}$. The highest bin in each histogram shows the number of events with $m_{t\overline{t}}>1175\mathrm{GeV}$.

Figure 3

Observed and expected upper limits on $\sigma B$ for a narrow $t\overline{t}$ resonance as a function of the resonance mass. The shaded regions around the expected limit represent the $\pm 1$ and $\pm 2$ standard deviation bands. The lines show predicted $\sigma B$ values for topcolor $Z^{\prime }$ bosons and for colorons.