RevModPhys.84.1477】Tests of the standard electroweak model at the energy frontier

Jets must have et 35 gev and the other must have et 25

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Unformatted text preview: No. 4, October–December 2012 FIG. 57 (color online). Expected and observed limits for the D0 0:45 fbÀ1 ZH ! ‘‘bb analysis. Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . 1518 TABLE XXXV. Definitions of the three regions (CR1, CR2, and ~ Signal) in the CDF VH ! ET bb search. ÁÈðET 1ð2Þ ; ET Þ is the angle 6 6 between the ET and the jet with the highest (second highest) ET . 6 Region Dominant source Selection CR1 Multijet CR2 " EW, tt Leptons vetoed ~6 ÁÈðET 2 ; ET Þ < 0:4 Lepton required ~6 ÁÈðET 2 ; ET Þ > 0:4 Leptons vetoed ~ 6~ ÁÈðET 1 ; ET Þ > 0:4 ~ 6~ ÁÈðET 2 ; ET Þ > 0:4 Signal multijet background is studied by dividing the sample into two control regions and a signal region. The regions are defined in Table XXXV. The multijet background in all regions is divided into two components: (1) events with only light-flavor (u, d, and s) quarks in which one or more of the jets is misidentified with a secondary vertex, and (2) events with c and b quarks. The contribution from lightflavor jets is determined using a control sample with no tags to which a misidentification factor is applied. The heavyflavor contribution is determined using simulated events with TABLE XXXVI. Yields in the CDF VH ! ET bb analysis. 6 Source Single tagged 93 Æ 23 27:3 Æ 3:8 7:0 Æ 1:4 33:4 Æ 16:2 18:3 Æ 8:1 69 Æ 9 248 Æ 43 268 Multijet " tt Diboson W þ hf Z þ hf Mistags Total Observed Double tagged 3:74 Æ 1:27 4:88 Æ 0:8 0:79 Æ 0:19 1:65 Æ 0:86 1:67 Æ 0:77 1:64 Æ 0:48 14:4 Æ 2:7 16 normalization factors for single-tag and double-tag topologies determined by forcing the data yields and the sum of all backgrounds to agree (before dividing the sample into the three regions). The scale factors are 1:30 Æ 0:4 (1:47 Æ 0:07) for the single (double) b-tagged events. The final analysis selection is determined by optimizing pffiffi S= ðBÞ where S is the total signal yield, including the contribution from WH ! ‘bb in which the lepton is not identified, and B is the total background. The optimization is carried out only for the signal region. The final selection then requires Áðj1 ; j2 Þ > 0:8, H T =HT > 0:454, Ej1 > 60 GeV, T and ET > 70 GeV. Here HT is the scalar sum of the jet ET 6 values, H T is the magnitude of the vector sum, and j1 (j2 ) denotes the jet with the highest (second highest) ET . The systematic uncertainties arise from a number of sources. For the CDF analysis the dominant uncertainty in the jet energy calibration which varies between 10% and 26% for multijet and V þ jets (including heavy-flavor) backgrounds, but is only 8% for signal events. The other dominant systematic arises from the calculated cross sections used to normalize backgrounds. This ranges between 11% and 40% for a given source depending on the samples. The total systematic is 17% for the single-tagged analysis and 19% for the double-tagged analysis. Figure 58 shows...
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