DOIAbstract
We measure the top quark mass mt using tt̅ pairs produced in the D0 detector by √s=1.8 TeVpp̅ collisions in a 125 pb-1 exposure at the Fermilab Tevatron. We make a two constraint fit to mt in tt̅→bW+b̅W- final states with one W decaying to qq̅ and the other to eν or μν. Events are binned in fit mass versus a measure of probability for events to be signal rather than background. Likelihood fits to the data yield mt=173.3±5.6(stat)±6.2(syst) GeV/c2