Search for $W^{\prime }$ Boson Resonances Decaying to a Top Quark and a Bottom Quark

We search for the production of a heavy $W^{\prime }$ gauge boson that decays to third generation quarks in $0.9{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed $W^{\prime }$ boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed $W^{\prime }$ bosons, we set lower mass limits of 739 GeV if the $W^{\prime }$ boson decays to both leptons and quarks and 768 GeV if the $W^{\prime }$ boson decays only to quarks. We also set limits on the coupling of the $W^{\prime }$ boson to fermions as a function of its mass.

Figure 1

$\sqrt{\widehat{s}}$ distributions for the data and the SM background. Plot (a) shows the $W_L^{\prime }$ signal, and plot (b) shows the $W_R^{\prime }$ signal at two different masses, normalized to the NLO prediction (Table 2). Events in the eight subsamples (electron, muon, two and three jets, single-tagged, and double-tagged) are combined.

Figure 2

NLO theory cross sections and 95% C.L. limits for ${\sigma }_{W^{\prime }}\times B(W^{\prime }\to tb)$ as a function of $W^{\prime }$ mass for (a) $W_L^{\prime }$ production and (b) $W_R^{\prime }$ production. Observed limits on the ratio of coupling constants $g^{\prime }/g_w$ are shown in (c). The shaded regions are excluded by this analysis.