1. Jet Veto Scale Factor for ZZ Analysis Haijun Yang, Lailin Xu, Bing Zhou ATLAS SM ZZ  Meeting February 2, 2012

2. Jet Veto Scale Factor from Data The scale factor of jet veto for ZZ  events between Data and MC can be measured using Z  events in Data and MC, it can be expressed by the equation, Require two same flavor leptons (ZZ  selection). Require |M -M Z | < 15 GeV to select Z  events. Using Jet veto with Et threshold >25 GeV and |  |<4.5 2011 Data integrated luminosity 4.7 fb -1 2

3. Jet Veto Efficiency and Scale Factor SamplesJet Veto Efficiency(%) (Et>25 GeV, |  |<4.5) Scale Factor = Eff_data / Eff_MC Data Zee79.87 ± 0.04 - MC@NLO Zee83.78 ± 0.090.953 ± 0.001 Alpgen Zee80.01 ± 0.040.998 ± 0.001 Pythia Zee78.23 ± 0.041.021 ± 0.001 3  Uncertainty from MC generators: (1.021+0.998) / 2 / 0.953 - 1 = 5.9%

4. Jet Veto Efficiency and Scale Factor SamplesJet Veto Efficiency(%) (Et>25 GeV, |  |<4.5) Scale Factor = Eff_data / Eff_MC Data Zee79.87 ± 0.04- MC@NLO Zee83.78 ± 0.090.953 ± 0.001 JER ON83.22 ± 0.080.960 ± 0.001 JES down86.44 ± 0.120.924 ± 0.001 JES up81.52 ± 0.130.980 ± 0.001 4  Uncertainty from JER and JES: 0.960 / 0.953 - 1 = 0.7% (JER) 0.924 / 0.953 - 1 = -3.0% (JES down) 0.980 / 0.953 - 1 = 2.8% (JES up)

5. Jet Veto Efficiency and Scale Factor SamplesJet Veto Efficiency(%) (Et>25 GeV, |  |<4.5) Scale Factor = Eff_data / Eff_MC Data Z  79.57 ± 0.03- MC@NLO Z  83.50 ± 0.080.953 ± 0.001 Alpgen Z  79.79 ± 0.030.997 ± 0.001 Pythia Z  77.95 ± 0.031.021 ± 0.001 5  Uncertainty from MC generators: (1.021+0.997) / 2 / 0.953 - 1 = 5.9%

6. Jet Veto Efficiency and Scale Factor SamplesJet Veto Efficiency(%) (Et>25 GeV, |  |<4.5) Scale Factor = Eff_data / Eff_MC Data Z  79.57 ± 0.03 - MC@NLO Z  83.50 ± 0.08 0.953 ± 0.001 JER ON83.50 ± 0.080.953 ± 0.001 JES down86.56 ± 0.100.919 ± 0.001 JES up81.80 ± 0.110.973 ± 0.001 6  Uncertainty from JER and JES: 0.953 / 0.953 - 1 = 0% (JER) 0.919 / 0.953 - 1 = -3.6% (JES down) 0.973 / 0.953 - 1 = 2.1% (JES up)

7. Summary Jet Veto scale factor for ZZ  is measured using Z   events, SF = 0.953 ± 0.001(stat) ± 0.059(MC) ± 0.036(JES)