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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

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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 ET

miss

ATL-COM-PHYS-2010-296 : ATLAS note on MC simulation of W production

u/t-channel s-channel

ISRFSR

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• 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 :

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Event Selection

Electron Muon

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

• ||<2.37 (no crack 1.37-1.52) , dR(e/,)>0.7

•Pt>15 GeV, pass OTX cut

•Tight Photon

•Isolation : EtCone20 (corrected for intime pileup and leakage)< 5 GeV

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• 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 :

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Electron channel : Electron channel :

Calo Photon isolation(GeV) Track Photon isolation(GeV)

Etcone20Ptcone20

Wγ analaysis: photon isolation

MC more isolated

• Use photon isolation distribution to estimate W+jet background from data. • Bigger discrepancy in Calo isolation

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Wγ analaysis: lepton and photon after tight +isolation photon selection

Muon channel :Electron channel :

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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

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Wγ analaysis: Number of jetsafter tight +isolation photon selection

Muon channel :Electron channel :

Pure MC based background estimationData 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|<4.4Overlap 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.

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η(γ)-η(e)

Electron channel : Muon channel :

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Photon Calo isolation(GeV) Photon Track isolation(GeV)

Photon pT[GeV]

Zγ analaysis: Photon pT and isolation

MC more isolated

Etcone20Ptcone20

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• Good agreement between data/MC

Zγ analaysis: MET and jets

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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

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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

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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

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M(γ;lepton)

pT(γ)

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• 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