Observation of the Top Quark

TL;DR

The paper reports the first observation of the top quark in proton-antiproton collisions at Fermilab, confirming its existence with significant statistical evidence and measuring its mass and production cross section.

Contribution

First experimental observation of the top quark, including measurement of its mass and production cross section in proton-antiproton collisions.

Findings

Observed 17 events with a low background expectation.

Measured top quark mass to be approximately 199 GeV/c².

Determined the top quark production cross section to be about 6.4 pb.

Abstract

The DO collaboration reports on a search for the Standard Model top quark in pbar-p collisions at Sqrt(s)=1.8TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50pb-1. We have searched for t-tbar production in the dilepton and single-lepton decay channels, with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8+/-0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2.0E-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199^+19_21 (stat.)+/- 22 (syst.)GeV/c**2 and its production cross section to be 6.4 +/- 2.2 pb.