1 W/Z  status report Standard Model meeting, Jun 22th 2011 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 (1)Duke University (2)Academia Sinica (3)University of Science and Technology of China (4)Moscow Engineering Physics Institute (5)CERN (6)Universities of California, Irvine (7)LAPP-Laboratoire d'Annecy-le-Vieux de Physique des Particules (8)Harvard University (9)University of Oxford (10)LBL

22 Introduction W+  production TGC Main background: W+jets (jet fakes as  ) Z+  /jets (one lepton not Id, jet mis-Id as  ) ttbar production 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 E T miss ATL-COM-PHYS : ATLAS note on MC simulation of W  production u/t-channel s-channel ISR FSR

3 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 Group Activities :

4 Event Selection ElectronMuon W Selection Cuts Egamma GRL, MET Clean-up EF_e20_medium(D~G5), 678pb-1 nVtx>=1 (nTrk>=3) Electron selection : Pt>25 GeV, |  |<2.47 (no crack), OTX cut, IsEM tight Z veto: no second medium electron MET>25 GeV, MT(e, )>40 GeV GRL, MET Clean-up Muon Trigger (B~G5), 690pb-1 nVtx>=1 (nTrk>=3, |Vz|<150mm) Muon selection : >=1 good muon Pt>20 GeV, |  |<2.4 MET>25 GeV, MT( , )>40 GeV Photon Selection Cuts |  | 0.7 Pt>15 GeV, pass OTX cut Tight Photon Isolation : EtCone20 (corrected for intime pileup and leakage)< 5 GeV

5 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 Electron channel : New Selection for Wγ analaysis: wrt to 2010 analysis Muon channel :

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

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

8 Wγ analaysis: MET after 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 jets after 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 Data driven BG shape agrees better MC based BG shape peak at 0 jet bin  Jet PT( EM+JES)>30GeV, |Eta|<4.4  Overlap removal with lepton and photon

Wγ analaysis: Radiation zero discovery 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. 10 η(γ)-η(e) Electron channel : Muon channel :

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

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

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

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 14

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 15

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 16 M(γ;lepton) pT(γ)

17 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. Summary