W/Z  status report

1. Al Goshaw(1) , Andrea Bocci(1) , Miaoyuan Liu(1) Zongjin Qian(1), Joshua Loyal(1) Song-Ming Wang(2) , Suen Hou(2) , Dong Liu(2), Zhili Weng(2) Ming-hui Liu(3)Evgeny Soldatov(4), Stephen Gibson(5) , Jianrong Deng(6) , Louis Helary(7) ,  Joao Barreiro Guimaraes Da Costa(8) Zhijun Liang(9), , Shih-Chieh hsu(10) , Kristian Gregersen W/Z status report Duke University Academia Sinica University of Science and Technology of China Moscow Engineering Physics Institute CERN Universities of California, Irvine LAPP-Laboratoire d'Annecy-le-Vieux de Physique des Particules Harvard University University of Oxford LBL Standard Model meeting, Jun 22th 2011

2. Introduction TGC • W+ production ISR FSR s-channel u/t-channel • W measurement can probe WW triple gauge boson coupling (TGC) vertex •  from s-channel tends to have higher Pt • If presence of anomalous TGC from new physics, could enhance W production rate, particularly at the high  Pt region. • Analysis : select events with 1 isolated lepton (e,) , 1 isolated photon, large ETmiss • Main background: • W+jets (jet fakes as ) • Z+/jets (one lepton not Id, jet mis-Id as ) • ttbar production : ATLAS note on MC simulation of W production ATL-COM-PHYS-2010-296 2

3. Group Activities : • Two group meeting per week, try to ramp up to full speed for EPS. • Lots of activities in Wγ/Zγ group recently: • Jet background estimation: Song-Ming, Zhili, Minghui • EM scale uncertainty : Dong Liu • Photon ID efficiency :Evgeny , Miaoyuan • Radiation zero discovery in Wgamma: Stephen • Data/MC comparison : Song-Ming, Zhili , Louis, Joshua • Plan for ATGC coupling study : ZL , Minghui, Kristian • New Sherpa signal sample validation • Compare Sherpa with Madgraph (Will) • Compare Sherpa with Baur (Kristian) • Electron channel cutflow comparison • Stephen , Zongjin, Miaoyuan ,ZL

4. Event Selection

5. New Selection for Wγ analaysis: wrt to 2010 analysis Muon channel : Electron channel : • Z+γ/Z+jet becomes main background in 2011 analysis due to high pileup envirnoment • Smooth mass distribution in high pT. • Hard to control the Z background in Electron channel • Due to electron fake as photon. • try to exclude Z peak region |M(e;g)-M_Z|>10GeV in electron channel

6. Wγ analaysis: photon isolation Photon Isolation Electron channel : Electron channel : MC more isolated Etcone20 Ptcone20 Calo Photon isolation(GeV) Track Photon isolation(GeV) • Use photon isolation distribution to estimate • W+jet background from data. • Bigger discrepancy in Calo isolation

7. Muon channel : Wγ analaysis: lepton and photon after tight +isolation photon selection Electron channel :

8. Wγ analaysis: METafter tight +isolation photon selection Muon channel : Electron channel : Pure MC based background estimation Data driven W+jet shape take from non-isolated/non-tight photon Agree better in medium/high pT

9. Wγ analaysis: Number of jetsafter tight +isolation photon selection Muon channel : Electron channel : • Jet PT( EM+JES)>30GeV, |Eta|<4.4 • Overlap removal with lepton and photon • Pure MC based background estimation • Data driven W+jet shape take from • non-isolated/non-tight photon • Data driven BG shape agrees better • MC based BG shape peak at 0 jet bin

10. Wγ analaysis: Radiation zero discovery Muon channel : Electron channel : • SM model predict a dip in η(γ)-η(lepton), but have not yet confirmed by any experiment. • reasonalble agreement between electron and muon channel , Data/MC in dip region (around Δη=0), • Try to extract 5 sigma significant from data to prove the existing of Radiation Zero dip. η(γ)-η(e)

11. Zγ analaysis: Photon pT and isolation MC more isolated Etcone20 Ptcone20 Photon Calo isolation(GeV) Photon Track isolation(GeV) Photon pT[GeV]

12. Zγ analaysis: MET and jets • Good agreement between data/MC

13. Zγ analaysis: Leading and sub-leading electron pT • Low pt region, MC/data agrees well

14. Baseline simple method for ATGC limit setting • Plan to extract ATGC coupling limit • C_W(C_Z): calculate efficiency factor as of photon pT • Efficiency Correction factor shows no dependence on ATGC coupling parameter. • Less than 5% difference between SM sample and ATGC sample • One full simulation is enough to calculate C_W[pT], • Don’t need full simulation for every ATGC grid points. • A_W(A_Z): • Show strong dependence on ATGC parameter. • Need to re-calculate for each ATGC points, need lots of generation

15. Baseline simple method for ATGC limit setting(Minghui) • σ[pT]: LO and NLO cross section for ATGC points. • Key point is to control k factor uncertainty in high pT region

16. ME re-weighting for ATGC study • A_W(A_Z) need lots of generation with normal method. • Kristian have tried ME weighting on this issue. • All contributoins 2->3 Wγ, 2->4 (Wγ+gluon jet ) 2->4 (Wγ+quark jet ) agrees well using re-weighting method • Discrepancy in Low M(photon;lepton) and low photon pT region due to FSR contribution is included in Baur • Low Mass/PT are not used in TGC study any way pT(γ) M(γ;lepton)

17. Summary • Two group meetings per week, have ramped up to full speed for EPS • Plan to write CONF note for EPS in two weeks. • 690pb-1 data(up to G5) data have been studied. • Lepton / Photon pT control plots have good agreement between data/MC . • MET/Jets distributions are better understood, data driven BG shape seems to work. • Angular distribution between lepton and photon have reasonable agreement between data/MC, electron/muon channel. • Two methods for ATGC limit : • Simple approach by breaking down observable( N_obs) into Acceptance , efficiency factor , cross section for ATGC 2D parameter grid • ME re-weighting , try to generate the observable ( N_obs) for the whole 2D parameter grid using a full simulated ATGC sample in one go.