1. E. Soldatov01.11.2011 Tight photon efficiency study using FSR photons from Z  ll  decays E.Yu.Soldatov 1, 1 National Research Nuclear University “MEPhI” Outline: 1.Motivation 2.Selection 3.Comparison of ID efficiency from ee  and  4.Data driven efficiency vs MC fudge factor corrected Wg/Zg informal meeting

2. E. Soldatov Introduction What do we want? The main idea is to obtain a photon sample with maximum purity with the method decoupled from the standard analysis methods. Why do we want this? Studies of the ATLAS detector performance with tagged photons and first of all study and optimization of the tight cut criteria. Very important for analysis all photon containing processes. The best source of such kind of photons is a production of FSR photons from Z-lepton decay: № 2№ 2 2010 results of this study gave first evaluations on tight efficiency from Z radiative decays: https://indico.cern.ch/getFile.py/access?contribId=7&resId=1&materialId=slides&confId=125163 Wg/Zg informal meeting01.11.2011

3. E. Soldatov № 3№ 3 Introduction: Samples Electron channel: MC: mc10_7TeV.106046.PythiaZee_no_filter.merge.AOD.e574_s933_s946_r2399_r2300/ Data: 2011 Periods D-H (Egamma stream) – 1.0 fb -1 (rel. 16 prod.) GRL: data11_7TeV.periodAllYear_DetStatus-v28-pro08-07_CoolRunQuery-00-04- 00_Eg_standard.xml Muon channel: MC: mc10_7TeV.106047.PythiaZmumu_no_filter.merge.AOD.e574_s933_s946_r2399_r2300/ Data: 2011 Periods D-H (Muons stream) – 1.0 fb -1 (rel. 16 prod.) GRL: data11_7TeV.periodAllYear_DetStatus-v28-pro08-07_CoolRunQuery-00-04- 00_WZjets_allchannels.xml 28.10.2011Wg/Zg informal meeting

4. E. Soldatov № 4№ 4 Introduction: Preselection The initial requirements are: Trigger for Z  ee  : EF_e20_medium Trigger for Z  : EF_mu18_MG || EF_mu40_MSonly_barrel First primary vertex with at least 3 tracks E T >5 GeV for photons, P T >15 GeV for electrons and muons, |  |<2.47 (|  |<2.4 for muons); excluding the crack region (1.37<|  |<1.52), Good object quality D0-to-PV and Z0-to-PV cuts (EPS) Electrons pass Medium cut deltaR(l  )>0.2 && preselection for leptons consistent with EPS recommendations applied MCTruthClassifier Tool used for truth matching 28.10.2011Wg/Zg informal meeting

5. E. Soldatov Introduction: Selection № 5№ 5 1. Mass of two leptons should have a missing part e.g. < Z bozon mass For electron channel 60 < m( ee ) < 83 GeV, and for muon channel 40 < m(  ) < 82 GeV A kinematic approach of the photon selection 2. And 3 body mass should correspond to a mass of Z bozon For electron channel 80 < m( ee  )< 94 GeV and for muon channel 81 < m(  ) < 95 GeV Kinematics approach is based on a simple criteria of the event selection. Three body mass spectrum (Z  ll  ) 3. Isolation: Etcone20_ptcorrected<5 GeV && Nucone20=0. 28.10.2011 Signal ( FSR ) Background ( Jets, Brem, ISR ) (More detailed cut study: https://indico.cern.ch/getFile.py/access?contribId=3&resId=1&materialId=slides&confId=92681) Wg/Zg informal meeting

6. E. Soldatov Tight cut efficiency study Comparison of the efficiency electrons and muons channels № 6№ 6 28.10.2011 convertedunconverted Wg/Zg informal meeting

7. E. Soldatov Tight cut efficiency study Comparision of data driven efficiency vs fudge factor corrected MC № 7№ 7 28.10.2011 convertedunconverted Z  Z  ee  Wg/Zg informal meeting

8. E. Soldatov Conclusions Efficiency study for data periods D-H (release 16) ~1 fb - 1 and mc10b using radiative Z decays (to electron and to muon channel) has been done. Comparison between electron and muon channel has been shown. It has just some differencies in the areas with the low statistics. Preliminar comparison of the data driven efficiency and fudge factor corrected MC has been presented. There are some differencies we need to discuss. № 8№ 8 28.10.2011Wg/Zg informal meeting

9. E. Soldatov Back-up slides № 9№ 9 28.10.2011Wg/Zg informal meeting

10. E. Soldatov Tight cut efficiency study Comparision of data driven efficiency vs fudge factor corrected MC № 10 28.10.2011 Z  ee  Z  combined Wg/Zg informal meeting

11. E. Soldatov Tight cut efficiency study Comparision of data driven efficiency vs fudge factor corrected MC № 11 01.11.2011 BarrelEndCap Z  Wg/Zg informal meeting