ar X iv : h ep - p h / 93 08 34 5 v 1 2 6 A ug 1 99 3 WHERE IS TOP ?

Possibilities are discussed for determining the top quark mass mt from observations on the decay processes for top-antitop pairs produced in antiproton-proton collisions at Tevatron energies, assuming that the t → bW decay channel is dominant and much faster than hadronization. The final states tt̄ → b̄bμe provide the most striking signal, with little background, but they are rare (≈ 2/81). If all three candidate events prove to be from tt̄, an estimate follows for P (mt | rate), the probability distribution for mt. The one reported configuration allows an independent estimate for P (mt | μe 2jets). These two distributions are compatible and can be combined to give an mt estimate of about 122 GeV. Decay events “1 energetic lepton(l) + 4jets” should appear twelve times as often as “μe 2jets” events and can be analysed to give estimates for P (mt | l 4jets); this is illustrated for a fictitious event. There may be background from non-top events but suitable cuts on the data and our analysis procedure together reduce this to a low level. The rate observed for these events does not appear to be as large as this factor 12. Identification of either or both of the (bb̄) jets would be a great step forward, separating out the “μebb̄” and “lbb̄ 2jets” events of importance with negligible background. We advocate an energetic approach to the analysis of individual events (whether 2,1 or no (b or b̄) jets identified) on an event by event basis, with the hope of finding a subgroup of events with a common mass estimate. This paper was given by the first author (R.H.D.) on 19 July 1992 at the International School of Subnuclear Physics at ERICE. Its text has been updated to the end of 1992.