Observation of the top quark with the D0 detector

The D0 collaboration reports on the observation of top quark in p{bar p} collisions at {radical}{bar s} = 1.8 TeV at the Fermilab Tevatron. We measure the top quark mass to be 199{sub -21}{sup +19}(stat.){sub -21}{sup +14}(syst.) GeV/c{sup 2} and its production cross section to be 6.4 {+-} 2.2 pb. Our result is based on approximately 50 pb{sup -1} of data. We observe 17 events with an expected background of 3.8 {+-} 0.6 events. The probability of an upward fluctuation of the background to produce the observed signal is 2 x 10{sup -6} (equivalent to 4.6 standard deviations). The kinematic properties of the events are consistent with top quark decay, and the distribution of events across the seven decay channels is consistent with the Standard Model top quark branching fractions. We describe the analysis that led to the observation of the top quark as well as the properties of the top quark events