We observe hadronic $W$ decays in $t\overline{t}\to W(\to \ell \nu )+\ge 4$ jet events using a $109{\mathrm{pb}}^{-1\mathrm{}}$ data sample of $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$ collected with the Collider Detector at Fermilab. A peak in the dijet invariant mass distribution is obtained that is consistent with $W$ decay and inconsistent with the background prediction by $3.3\sigma$. From this peak we measure the $W$ mass to be $77.2\pm 4.6(\mathrm{stat}+\mathrm{syst})\mathrm{GeV}{/c}^2$. This result demonstrates the presence of a second $W$ boson in $t\overline{t}$ candidates in the $W(\to \ell \nu )+\ge 4$ jet channel.

• Received 29 December 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.5720