w/z status report
DESCRIPTION
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) , - PowerPoint PPT PresentationTRANSCRIPT
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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