CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

two or more, and events with E miss
T
< 20 GeV, are used. In events with Emiss T < 20 GeV, 11 2ID+TL events
are observed and 14.4 ± 0.4 predicted by the fake matrix, plus the other backgrounds. In one-jet events,
9 2ID+TL events are observed and 15.3 +0.9
−1.0 predicted. The results are shown in Table 7.3, and Table 7.4
respectively. These numbers are also plotted in the first two bins of Figure 5.9(a), and the one-jet bin of
Figure 5.9(b), respectively. The final column is the fractional difference between the total background pre-
diction (including WZ, ZZ and t¯t+W/Z events) and the observation, normalized to the fake TL prediction.
Low E miss
T
Control Region
E miss
T ZZ and WZ t¯tW and t¯tZ fake TL Prediction B O (B − O)/P
0-10 GeV 0.04 ± 0.02 0.01 +0
−0 4.9 ± 0.1 4.9 ± 0.1 4
10-20 GeV 0.4 ± 0.2 0.04 +0.01
−0.01 9.1 ± 0.2 9.5 ± 0.3 7
≤ 20 GeV 0.4 ± 0.2 0.06 +0.01
−0.01 13.9 ± 0.3 14.4 ± 0.4 11
+23.8
24.7 −23.9 %
Table 7.3: The predicted and observed fake TLs in two bins of E miss
T . The last column is the total background
prediction, minus the data observation, divided by the fake prediction. The uncertainties on the fakes are
statistical only, whereas the uncertainties in the other background are statistical and systematic.
1 jet Control Region
ZZ and WZ t¯tW and t¯tZ fake TL Prediction B O (B − O)/P
+22.9
9 46.4 −23.0 %
1 jet 1.7 +0.8
−0.9 0.04 ± 0.01 13.6 ± 0.4 15.3 +0.9
−1.0
Table 7.4: The predicted and observed fake TLs in events with exactly one b-tagged jet. The last column is the
total background prediction, minus the data observation, divided by the fake prediction. The uncertainties on
the fakes are statistical only, whereas the uncertainties in the other background are statistical and systematic.
Althought the predicted minus observed is somewhat larger than the 20% uncertainty derived in the
W+jets CR and the results shown in Table 7.2, it is not inconsistent given the total of only 20 events
observed in this case. Thus, a 20% systematic uncertainty on the fakes prediction is used in this analysis.
An additional check for TLs coming from conversions is done on MC, and it is estimated to be less than
3%. This effect should be covered by the systematic uncertainty just quoted. No additional systematic
uncertainty is taken for the possible effect of b-tagging on the fake TL prediction, which might be expected
due to the enhanced heavy-flavor fraction of b-tagged events. No need for this is seen in the low E miss
T
one-jet CRs, and moreover consistent fake rates between data and MC for both heavy- and light-flavor jets
are observed.
88
and