Observation of Top Quark Production in Pbar-P Collisions

Abstract

We establish the existence of the top quark using a 67 pb^-1 data sample of Pbar-P collisions at Sqrt(s) = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with t-tbar decay to WW b-bbar, but inconsistent with the background prediction by 4.8 sigma. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be 176 +/-8(stat) +/- 10(sys.) GeV/c^2, and the t-tbar production cross section to be 6.8 +3.6 -2.4 pb.

Figures (3)

• Figure 1: Number of events before SVX tagging (circles), number of tags observed (triangles), and expected number of background tags (hatched) versus jet multiplicity. Based on the excess number of tags in events with $\ge3$ jets, we expect an additional 0.5 and 5 tags from $t\bar{t}$ decay in the 1 and 2 jet bins respectively. The inset shows the secondary vertex proper time distribution for the 27 tagged jets in the W + $\ge3$-jet data (triangles) compared to the expectation for $b$ quark jets from $t\bar{t}$ decay.
• Figure 2: Reconstructed mass distribution for the W + $\ge4$-jet sample prior to $b$-tagging (solid). Also shown is the background distribution (shaded), with the normalization constrained to the calculated value.
• Figure 3: Reconstructed mass distribution for the $b$-tagged W + $\ge4$-jet events (solid). Also shown are the background shape (dotted) and the sum of background plus $t\bar{t}$ Monte Carlo for $M_{top} = 175$ GeV/c$^2$ (dashed), with the background constrained to the calculated value, $6.9^{+2.5}_{-1.9}$ events. The inset shows the likelihood fit used to determine the top mass.