2 The CDF Experiment at Fermilab Contents - Harvard University ...

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52 Section 2: CDF Physics Analysis 60 Events with SECVTX tags Events without SECVTX tags 50 JPB tags data 100 JPB tags data Number of tagged events 40 30 20 Top QCD Number of tagged events 80 60 40 Top QCD 10 20 0 1 2 3 ≥4 Number of jets 0 1 2 3 ≥4 Number of jets Figure 26: Comparison of the observed and predicted rates of JPB tags in events with and without SECVTX tags. The predictions are based on the W sample composition determined by the measurement of the tt cross section with SECVTX. Direct production of W +jets without heavy avor. Most of the events due to W + c b and Wc production, since SECVTX is less ecient for tagging c-quark jets. Events due to Wb b production when the b-jets are not taggable (SECVTX is more ecient for tagging b-jets than JPB and SLT). Rates of observed and expected JPB tags in the two samples are shown in Figure 26. In the W + 2 jet events tagged by SECVTX, the observed number of JPB tags agree with the expectations. The excess is 6:027:67 events. In the remaining W + 2 jet events, there is an excess of JPB tags of 20:26:1 events. This excess is as large as the total number of tt events tagged by SECVTX (21.1 events). It could be explained by a miscalculation of the Wcc and Wc contributions or by a W + c-jets production process unaccounted by the Standard Model. On one hand, the good agreement between the observed and predicted rates of JPB tags in W +1jet events (which are dominated by Wc and Wcc production)
Section 2: W Mass 53 Number of tagged events 12 10 8 6 4 Events with SECVTX tags SLT tags data Top QCD 2 0 1 2 3 ≥4 Number of jets Figure 27: Comparison of the observed and predicted rates of SLT tags in events with SECVTX tags. The predictions are based on the W sample composition determined by the measurement of the tt cross section with SECVTX. seems to exclude a mistake in the predictions. On the other hand, since the tagging eciency of JPB for c-jets is a factor of two smaller than the tagging eciency of SECVTX for b-jets, it implies that the new W + c-jets production mechanism will have a cross section a factor two larger than tt production. For the SLT, it is useful to compare observed tags to expectations only in the sample tagged by SECVTX since the sample without SECVTX tags has too much background. The rates of observed and predicted SLT tags are shown in Fig. 27. In the W + 2 jet sample tagged by SECVTX, there is an excess of 7:33:3events to be compared with an expectation of 5.3 top events. So, in the SLT case, there is no sign of a discrepancy, within the large statistical uncertainty. Still we are studying the kinematic features of these events and nd some surprising features which cannot easily be explained by Standard Model processes. More work is required before we fully unravel the mysteries behind these fascinating anomalies. An article for Physical Review reporting the cross section measurements given above is planned. These cross-sections have been recently blessed by the CDF Collaboration.
Page 1 and 2: 1 2 The CDF Experiment at Fermilab
Page 3 and 4: Section 2: CDF 3 of Run I data. Rec
Page 5 and 6: Section 2: CDF Hardware Projects 5
Page 7 and 8: Section 2: Central Outer Tracker 7
Page 21 and 22: Section 2: DAQ for the Silicon Vert
Page 27 and 28: Section 2: Central Muon Extension 2
Page 33: Section 2: Central Muon Extension 3
Page 36 and 37: 36 Section 2: CDF 2.3 Run I Physics
Page 38 and 39: 38 Section 2: CDF Physics Analysis
Page 93 and 94: Section 2: B Mixing and CP Violatio
Page 95 and 96: Section 2: B Mixing and CP Violatio
Page 97 and 98: Section 2: CDF 97 multijet trigger
Page 99 and 100: Section 2: CDF 99 The Jet Pseudora
Page 101 and 102: Section 2: CDF 101 while the proble
Page 103 and 104:
Section 2: CDF 103 Talks at Confere
Page 105 and 106:
Section 2: CDF 105 References [1] T
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