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W/Z SM approval report Al Goshaw(1) , Andrea Bocci(1) , Miaoyuan Liu(1)

Will DiClemente(1),, Zongjin Qian(1), Joshua Loyal(1)

Song-Ming Wang(2) , Suen Hou(2) , Dong Liu(2), Zhili Weng(2)

He Liang(3), Hongye Song(3) , Ming-hui Liu(3),Evgeny Soldatov(4),

Stephen Gibson(5) ,Louis Helary(6), Tian Feng(7) , Zhijun Liang(8),

(1) Duke University

(2) Academia Sinica

(3) University of Science and Technology of China

(4) Moscow Engineering Physics Institute

(5) CERN

(6) LAPP-Laboratoire d'Annecy-le-Vieux de Physique des Particules

(7) Columbia University

(8) University of Oxford

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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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Event SelectionW Z•W/Z GRL, MET Clean-up (only for W), nVtx>=1

•Trigger : EF_e20_medium (electron), period D~H, 1fb-1

•EF_mu18_MG or EF_mu40_MSonly_barrel(muon)

•1 Electron: Tight, pT>25GeV, E_iso<6GeV•1 Muon :

•Combined Staco, PtCone20/Pt<0.1•Pt>25 GeV, MCP quality cuts

•MET_Lochadtopo>25 GeV• MT(lepton,)>40 GeV•Z veto for e channel: |M(e, )-M_Z|>10GeV

•2 Electron:

Medium, pT>25GeV•2 Muon :

•Combined Staco, •PtCone20/Pt<0.1•Pt>25 GeV, MCP quality cuts

•Opposite charged, M(l,l)>40 GeV

Photon Selection Cuts• IsEM Tight, Pt>15 GeV, dR(e/,)>0.7• Isolation : EtCone30_Pt_ED_corr < 6 GeV

Jet selection cuts •Anki KT 4 jets , pT(EM+JES)>30GeV, ||<4.4•dR(jet ,)>0.6, dR(jet ,leptons)>0.6

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W+jet background in Wγ analysis

Photon isolation in data is systematically higher than isolation in MC Data driven W+jet background estimation

Non-tight Control region to obtain photon isolation template for W+jet : Require photon candidates to fail at least two strip layer photon ID cuts

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Z+jet background in Zγ analysis

Lepton isolation and photon jet background

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Observe excess in data on lepton in lepton isolation distribution Indication of photon jet background in both electron and muon channel. The feature of photon jet background :

No real Missing ET Bad Lepton isolation , lepton is from jet fake Good photon isolation, photon is real Mostly from heavy flavor (γ+b/c jet) for muon channle

Background shape : Control region for Electron channel :

low MET region ( loose ,non-medium electron) Control region for Muon channel :

low MET region High pT Lepton track with large impact parameter (heavy flavor)

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Control regoin definition :Systematics of Wjet (Zjet) / γjet background

Wjet

γjet

Varying Non-tight defintion:failed at least two strip cutsfailed at least one strip cutsfailed at least three strip cuts

Varying Non-isolated defintion:E_iso(γ)>7GeVE_iso(γ)>8GeVE_iso(γ)>6GeV

Nomial: Nomial:

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2D sideband Systematics: correlations between two discriminating variables

Wjet

γjet

2D sideband assume no correlations photon shower shape and photon isolation Study such corrections for fake photons in Wjet background Monte Carlo

Define Rwjet as correlation factor, Rwjet =1 means no correlation. Rwjet in MC is consistent with 1 within 2~3 sigma Take the maximum variations of Nwjet as systematic (w/wo considering Rwjet )

2D sideband assume no correlations between MET and lepton isolation Study such corrections in γjet dominated control region in data

Define Rγjet as correlation factor, Rγjet =1 means no correlation. Study Rγjet in γjet dominated control region in data:

EF_2g20_loose trigger , at least one tight+ isolated photon At least one loose and failed medium electron.

Take the maximum variations of Nγjet as systematic (w/wo Rγjet )

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Background estimation summary

Wγ

Zγ

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Wγ control plot : photon pT

=0jet >=0jet Electron channel Muon channel

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Wγ control plot : lepton pT and MET

=0jet >=0jet Electron channel Muon channel

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Zγ control plot

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Phase space definition

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Photon efficiency uncertainty

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Uncertainty on Electron isolation efficiency

Data driven isolation efficiency measurement Select Z->e+e- events using electron tight cut Only use leading electron for study Rather pure electron sample >99% purity

In time pileup : study with different Number of primary vertex

Out-of-time pileup : study with candidates with different Bunch trains positions

pT dependence

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Uncertainty on Photon isolation efficiency

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JET/ MET acceptance uncertainty

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Overall uncertainty on detector effect

Electron channel

Muon channel

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Overall uncertainty on acceptance

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Parton and particle level SM prediction

Use MCFM to obtain SM NLO prediction in parton level

Correct them to particle level

Systematic uncertainty from parton to particle corrections

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Wg Cross section measurement result ( low pT region)

=0jet >=0jet

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Wγ Cross section measurement result ( medium pT region)

=0jet >=0jet

Electron channel Muon channel

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Wg Cross section measurement result ( high pT region)

=0jet >=0jet

Electron channel Muon channel

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Zg Cross section measurement result

=0jet >=0jet

Electron channel Muon channel

pT>15GeV pT>60GeV

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SM (inclusive)SM (0jet)

Summary of fiducial cross section

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TGC

u/t-channel s-channel

Anomalous coupling limit •W+ production

•Z+ production

• Z-Z-γ (Z-γ-γ) coupling is forbidden in SM model

• h3_γ and h4_γ are coupling parameter for Z-Z-γ

• H3_Z and h4_Z are coupling parameter for Z-γ-γ

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Δκ=0.4 (0jet)SM (0jet)

Anomalous coupling limit in Wγ

Use highest pT bin in fiducial measurement for ATGC study

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Bayesian limit setting

: ATGC Hypothesis

Lower limit

Upper limit

: possibility of one certainty ATGC Hypothesis given our Measurement as input

: input from fiducial measurement

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Background estimation in high pT region

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Systematics coupling limit in Wγ

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Result of ATGC in Wγ

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Systematics coupling limit in Zγ

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Result of ATGC in Zγ

Backup

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Systematics coupling limit in Wγ

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MC Samples for Signal & Jet Faking Photon BackGround

•Wgamma : AlpgenJimmyWgammaNpX (117410-117415)

•Normalize AlpgenNp(Np0+Np1) to Sherpa_Wmunugamma(0+1jet)

•Get k-factor=1.488, apply to all Alpgen samples( Np0~Np5)

•Cross section(by summing up Np0 ~Np5) = 83.2 pb

•Zgamma : Sherpa_Zmumugamma(0+1jet) (126016)

•Use cross section from Sherpa = 14.7 pb

•Jet Faking photon : using data-driven method for normalization

•Take shape from non-tight photon control region

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Jet multiplicity for Zg

pT>15GeV pT>60GeVpT>15GeV pT>60GeV