Improving the measurement of the top quark mass

Two possible ways to improve the mass resolution for observing hadronic top quark decay t\ensuremath{\rightarrow}bW\ensuremath{\rightarrow}3 jets are studied: (1) using fixed cones in the rest frames of the t and W to define the decay jets, instead of the traditional cones in the rest frame of the detector; and (2) using the jet angles in the top rest frame to measure ${\mathit{m}}_{\mathit{t}}$/${\mathit{m}}_{\mathit{W}}$. By Monte Carlo simulation, the second method is found to give a useful improvement in the mass resolution. It can be combined with the usual invariant mass method to get even better mass resolution. The improved resolution can be used to make a more accurate determination of the top quark mass, and to improve the discrimination between tt\ifmmode\bar\else\textasciimacron\fi{} events and background for studies of the production mechanism. \textcopyright{} 1996 The American Physical Society.