Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

TL;DR

This paper reports the observation of hadronic W decays in top-antitop events using Fermilab's Collider Detector, providing evidence for W bosons in these events and measuring their mass.

Contribution

First observation of hadronic W decays in t-tbar events at Fermilab, with a measured W mass consistent with expectations.

Findings

Dijet mass peak consistent with W decay

W mass measured as 77.2 +- 4.6 GeV/c^2

Evidence of W bosons in t-tbar candidate events

Abstract

We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). 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 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.