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Call for Acceptance challenge in W/Z+gamma analysis 2011

Zhijun Liang

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Introduction

•Base line cuts are being setup.

•Wiki:

•First important task is to converge on Acceptance challenge on DATA/MC.

•Welcome more new people to join this analysis

•Stephen Gibson (CERN), Elzbieta show interested in electron channel.

• Marcos shows interested in muon channel.

•Jianrong Deng shows interested in new channel Z(nunu)+gamma

https://twiki.cern.ch/twiki/bin/view/AtlasProtected/BaslinecutsforWZgammaforEPS2011

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Event Selection

W(enu)+gamma Z(ee)+gamma

•Egamma stream with GRL

• MET Clean-up

•EF_e20_medium

•nVtx>=1 (nTrk>=3)

•Electron selection :

•Pt>25 GeV, ||<2.5 (no crack), OTX cut, IsEM Medium plus plus

•Z veto: no second medium electron

•MET>25 GeV, MT(e,)>40 GeV

•Egamma stream + GRL

•nVtx>=1 (nTrk>=3)

•EF_e20_medium

• Two medium plus plus electron

•M(ee)>40GeV

•Electron selection :

•Pt>25 GeV, ||<2.5 (no crack), OQ cut, IsEM medium plus plus

Photon Selection Cuts

• ||<2.5 (no crack 1.37-1.52) , dR(e/,)>0.7

•Pt>15 GeV, pass OQ cut

•Tight Photon

•Isolation : EtCone40 _PtCorr< 12 GeV

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Definition of Medium plus plus electron ID cut: https://svnweb.cern.ch/cern/wsvn/atlasoff/Reconstruction/egamma/egammaAnalysis/egammaAnalysisUtils/trunk/src/IsEMPlusPlusDefs.cxx

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Backup

77

Data Cut Flow(177pb-1)

Z+gamma # Events

Z selection +

Photon: ||<2.5 (no crack), dR(,)>0.7 and Pt()>15 GeV

1087

Pass photon loose cut 228

Pass photon tight cut 89

Isolation : EtCone40<12 GeV 81

M(e+;e-;gamma)>110GeV 48

W+gamma # Events

W selection +

Photon: ||<2.5 (no crack), dR(e,)>0.7, Pt()>15 GeV,OQ check

8868

Pass photon loose cut 1470

Pass photon tight cut 545

Isolation : EtCone40<12 GeV

480

MT(e;nu;gamma)>100GeV

101

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Z+gammaW+gamma

Electron isolation(177pb-1)

•WW analysis proposed is too hard for W/Z+gamma analysis

•Not proposed to use isolation cut for electron before more understanding

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Photon isolation(177pb-1)

Z+gammaW+gamma

Blue curve : cut threshold used 2011

Red curve : proposed cut threshold

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Photon pT distributionv

Z+gammaW+gamma

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Radiation zero signal in W+gamma (177pb-1)

MT(e;nu;gamma)>100GeV

Phys Rev Lett. 2008 Jun 20;100(24):241805

No cuts on MT

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Two dimensional mass in Z(ee)+gamma(177pb-1)

FSR

ISR

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Summary

•Based line cuts have been setup.

•More people are joining this analysis .

•First look into the W/Z+gamma candidates in data.

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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