Improving the Measurement of the Top Quark Mass

Two possible ways to improve the mass resolution for observing hadronic top quark decay $t \to bW \to 3 jets$ 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 $m_t/m_W$. 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 an even better mass measurement. The improved resolution can be used to make a more accurate determination of the top quark mass, and to improve the discrimination between $t \bar t$ events and background for studies of the production mechanism.