We present a search for tt production in events having dielectron final states in 120.2 ± 6.5 pb -1 of pp collisions at s = 1.8 TeV using the DØ detector. This analysis has been optimized to search for a heavy top quark (ie. m top > 140 GeV/c 2 ). One candidate event is seen with a background estimated to be 0.82 ± 0.08 events, giving a cross section of 0.9 ± 5.0 pb if m top = 170 GeV/c 2 . Therefore, no conclusive evidence for top production is seen in this channel. Assuming the candidate is

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... t top, we obtain an upper limit to the dielectron branching ratio for tt events to be < 3.8 % at the 95% confidence level if m top = 170 GeV/c 2 . In the process of this analysis we have studied the reponse of the DØ U/LAr calorimeter to jets using direct photon candidate events. A number of systematics have been studied which result in a cumulative systematic error which varies from 5% at low and high energy (10 GeV and 500 GeV, respectively) to 2% at 80 GeV. The response to jets relative to the electromagnetic scale is found to behave as 0.77 + 0.024 * ln(E jet ) as expected from test beam and Monte Carlo studies.