Search for the Production of Narrow $t\overline{b}$ Resonances in $1.9{\mathrm{fb}}^{-1}$ of $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We present new limits on resonant $t\overline{b}$ production in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, using $1.9{\mathrm{fb}}^{-1}$ of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a candidate $t\overline{b}$ mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous $t\overline{b}$ production as modeled by $W^{\prime }\to t\overline{b}$. We set a new limit on a right-handed $W^{\prime }$ with standard model-like coupling, excluding any mass below $800\mathrm{GeV}/c^2$ at 95% C.L. The cross section for any narrow, resonant $t\overline{b}$ production between 750 and $950\mathrm{GeV}/c^2$ is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the $W^{\prime }$ coupling strength versus $W^{\prime }$ mass over the range $300–950\mathrm{GeV}/c^2$.

Figure 1

$M_{t\overline{b}}$ for events with two jets and one $b$ tag, comparing the shapes between background and signal. Backgrounds are stacked and grouped according to similar shape. A $600\mathrm{GeV}/c^2$ $W^{\prime }$ model is shown with $\sigma \times \mathrm{BR}(W^{\prime }\to t\overline{b})=9\mathrm{pb}$ ($\sim 4\times$ the prediction for a $W^{\prime }$ with SM-like coupling).

Figure 2

Expected and observed 95% C.L. limits on $\sigma \times \mathrm{BR}(W^{\prime }\to t\overline{b})$ as function of $M_{W^{\prime }}$ for $1.9{\mathrm{fb}}^{-1}$, along with theoretical predictions. A right-handed $W^{\prime }$ with SM-like couplings is excluded for $W^{\prime }$ masses below $800\mathrm{GeV}/c^2$.

Figure 3

Observed 95% C.L. limits on the coupling strength of a right-handed $W^{\prime }$ compared to the SM $W$ boson coupling, $g_{W^{\prime }}/g_W$, as function of $M_{W^{\prime }}$ for $1.9{\mathrm{fb}}^{-1}$. The shaded region above each dashed line is excluded.