Study of ppStudy of pp→→ZγZγ→→ee++ee--γ analysis at CMSγ analysis at CMS

Pooja SaxenaShilpi jain, Dr. Satyaki Bhattacharya, Dr. Kirti Ranjan

Research ScholarCDRST, Delhi University

India CMS meet, University of Delhi, 22th December 2011

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1. Motivation

2. Introduction to Zγ channel– Signal and background – Datasets

3. Results and Plots– Electron/photon selection– Discriminating variables– Kinematic distribution– Data MC matching

4. Summary & future plans

OutlineOutline

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MotivationMotivation

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The physics with diboson (WW, WZ, Zγ, ZZ, γγ) in the final state:

– Important test for SM

– Background for major Physics process

– Sensitive to physics beyond SM

(Anamolous ZγV(V= Z,γ) TGCs lead different cross section and kinematics)

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ZZγγ signature signature

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PRODUCTION MECHANISMS

Standard Model

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ZZγγ signature signature

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PRODUCTION MECHANISMS

Standard Model New Physics

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ZZγγ signature signature

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PRODUCTION MECHANISMS

Study of the dileptonic decay mode of Z process is a particularly promising one.

– Allows for a high experimental precision with a clean and easy-to analyze final state.

– Good tool to calibrate the detector

– Total cross section can be used as the luminosity candle at LHC

Use Leptonic decay Mode: e+e-

Standard Model New Physics

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BackgroundBackgroundWW WZ ZZ

WjetsZjets

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At Tevatron (CDF, PRL 2005)* :– The cross sections and boson production kinematics, are found to agree

with SM predictions. σ( p¯p → Zγ → e+e−γ) = 4.8 ± 0.8(stat.) ± 0.3 (syst.)± 0.3 (lumi.) pb

– The SM theoretical prediction for σ(Zγ → e+e−γ) = 4.5 ± 0.3 pb

At CMS (PLB, 2011)** : – Measurement of Zγ production in pp collisions at COM= 7 TeV, L = 36

pb-1

σ(pp → Z γ → e+e− γ) = 9.5 ± 1.4 (stat.) ± 0.7 (syst.) ± 0.4 (lumi.) pb– The SM theoretical prediction is 9.6 ± 0.4 pb

Ongoing CMS :– Measurement & study of Zγ production at 755 pb-1( draft note is available :

CMS AN_11_251v6)

The Preliminary study is to verify the selection criteria and to validate these results with the latest available results

Current StatusCurrent Status

8 Pooja saxena* http://prl.aps.org/abstract/PRL/v94/i4/e041803** http://cdsweb.cern.ch/record/1350795/files/PhysLettB.701.535.pdf

Data and MC SamplesData and MC Samples

Data

- DataSet: /DoubleElectron/Run2011A-May10ReReco-v1/AOD

/DoubleElectron/Run2011A-PromptReco-v4/AOD

- RunRange 160431-166861

- HLT used HLT_Ele17_CaloIdL_CaloIsoVL_Ele8_CaloIdL_CaloIsoVL_v*

- Json Cert_160404-163869_7TeV_May10ReReco_Collisions11_JSON.txt,

Cert_160404-166861_7TeV_PromptReco_Collisions11_v4_JSON.txt

- Integrated luminosity: 755 pb-1

Following VGamma Note : CMS AN-11-251 v6

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Data and MC SamplesData and MC Samples

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Process σ(pb) Dataset Name (AODSIM data tier)

Zγ→ e+e−γ 13.79 Privately produced using Madgraph + pythia

Zjets 2475 /DYJetsTOLL_TuneZ2_M-50_7TeV-madgraph-tauola

WW 43 /WW_TuneZ2_7TeV_pythia6_tauola

WZ 18.2 /WZ_TuneZ2_7TeV_pythia6_tauola

ZZ 5.9 /ZZ_TuneZ2_7TeV_pythia6_tauola

Wjets 31314 /WJetsToLNu_TuneZ2_7TeV-madgraph-tauola

MC (summer11)

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Photon/electron Selection Photon/electron Selection 1. One photon with Et > 15 GeV

2. dR(e,γ) > 0.7

3. ECAL fiducial region,

|η | < 1.4442 & 1.566 < |η | < 2.5

4. Isolation Variables

- Ecal Isolation < 4.2 + 0.006 x Et

- Hcal Isolation < 2.2 + 0.0025 x Et

- Track Isolation < 2 + 0.001 x Et

- H/E < 0.05

- σiηiη

< 0.011(EB), 0.030(EE)

5. Track Veto – require no pixel seed

6. Run based correction & rho correction

are added 11

1. Two electron with pt > 20 GeV within ECAL acceptance

|η | < 1.4442 and 1.566 < |η | < 2.5

2. To suppress Jets misidentified as electron,

|d0| < 0.02 cm & |dz| < 0.1 cm

3. Run based Correction are added.

4. Satisfy WP85 with rho correction

5. Mee

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Results Results atat

L = 755 pbL = 755 pb-1-1 @ 7TeV @ 7TeV((VGamma draft Note :VGamma draft Note : CMS AN_11_251v6 CMS AN_11_251v6))

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Entries SummaryEntries Summary

Difference of 174,

in discussion with group members

** Zjets background is not being included in the plots.

- Study of Data Driven (template method) is in progress.

CMS AN_11_251 CMS AN_11_251 My analysis

data 708 534

Zγ→e+e−γ 554.9 466.581

Zjets 123.5 **

WW+WZ+ZZ+Wjets minimal 3.119

Total MC 667.6 469.7

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Plots cntd..Pt & Pt & η η of of γ γ

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CMS AN_11_251CMS AN_11_251 Reproduced plot

Zee = Zγ → e+e-γ Others = WW+WZ+ZZ+Wjets

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Zγ → e+e-γZjetsOthers

data

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Plots cntd..Pt & Pt & η η ofof e- e-

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Photon Isolation VariablesPhoton Isolation Variablesa.) Ecal Isolation b.) Hcal Isolation c.) Track Isolation

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Barrel

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MeeMee

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CMS AN_11_251CMS AN_11_251 Reproduced plot

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MeeMee

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CMS AN_11_251CMS AN_11_251 Reproduced plot

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ISR

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MeeMee

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CMS AN_11_251CMS AN_11_251 Reproduced plot

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ISRFSR

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MeeMeeγγ

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Reproduced plot CMS AN_11_251CMS AN_11_251

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FSR

ISR

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Mee vs MMee vs Meeeeγγ

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Reproduced plot CMS AN_11_251CMS AN_11_251

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MeMeγγ

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Summary Summary – The present study was aimed for understanding of analysis &

validation of code with the ongoing work.– Studying the theory of Zγ physics– Analysing 755 pb-1 of data at COM 7 TeV– Compared the Data & MC for Zγ samples wrt kinematic

distributions and discriminating distributions.– Reproduced some of the plots of Zγ draft note (CMS

AN_11_251v6).

Future PlansFuture Plans– To resolve the data entries difference, in discussion with Zγ

group members.– To estimate fake photon background using data driven

techniques using template method.– Will perform the analysis with higher luminosity.– Setting up limit calculation tool and systematic study.– Will do the DQM shifts at CMS.

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ThanksThanks

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BACK-UP Pooja saxena

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Trigger SelectionTrigger Selection

L1 seed : SingleEG12

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Cross section

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Anamolous CouplingAnamolous Coupling

1. Lorentz and gauge invariant vertex described by 4 parameters : h

iV( i = 1, 2, 3, 4 ; V= γ, Z)

2. Couplings hiV with i=1, 2 violate CP symmetry &

for i=3, 4 are CP-even.

3. At tree level (SM), all the couplings vanish. But at one-loop level the CP-conserving Couplings are nonzero.

4. Measurement of h3V and h

4V for ZZγ and Zγγ are

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Anamalous Coupling cntd..Anamalous Coupling cntd..1. Tevatron

2. LHC (CMS)

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ThanksThanks

No of VertexNo of Vertex

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Cross Section vs M

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DiBoson at CDF

1. pp bar at COM - 1.96 TeV.

2. All agree with SM

Cdf, 2008 CFD7597_TANIMOTO Pooja saxena

Triple Gauge Coupling

1. possible trilinear gauge coupling involving the EW gauge boson W,Z,Y are

WWY, WWZ, ZZZ, ZZY, ZYY

2. In S.M, only WWY, WWZ are allowed whereas the neutral trilinear coupling ZZZ, ZZY, ZYY are all zero at tree level.

3. The measurement of the gauge boson pair production and te anamolous coupling provides an important test of EW gauge theory in SM. Any deviation will provide important inforamtion about the new physics beyond SM

Cdf, 2008 CFD7597_TANIMOTO

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1. L1 seed – SingleEG(12)

2. Identification variables:

• H/E = 0.05

• Sigma(ieta,ieta) = 0.011(BB) 0.031(EE)

• delta(eta) = 0.008(BB) 0.008, EE)

• delta(phi) = 0.07(BB) 0.05(EE)

Trigger Information(L1)

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|nieie| Shower shape variable

|n| is the n-n element of the n-phi covriance matrix, which provides another expression for the extent in n of the S.C.

- it is calculable with logarithmic weight and relative to E5x5 instead of SC energy

-it is given as:

- Ei and ni are the energy and “n” index of the ith cystal within 5x5 ecal cluster

- E5x5 is energy of 5x5 cystals around seed cystals

σ inin =Σw i (n i−nseed )

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Σw i

,

wi =max (0,4 . 7+lnE i

E5x5)

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Photon IdentificationPhoton Identification

- Photon candidates are reconstructed from energy deposits in the ECAL called as superclusters.

• Superclusters are formed from the energy sum clustered in a rectangle of crystals 35 wide in φ and 5 wide in η

• Superclusters allows almost complete recovery of energy deposited by photons.

- It is required that the signals be in time with the collision.

- Sum of energy in the four adjacent crystals surrounding the central crystal should be at least 5% of the central crystal’s energy.

- It is required to be in the pseudo rapidity acceptance of the tracker.

- It should not match pixel hits consistent with an electron or positron track from the interaction region.

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Photon IsolationPhoton IsolationIsoECAL : the sum of the transverse energy deposited in the ECAL in an annulus 0.06 < R

< 0.40, excluding a rectangular strip of deta x dphi = 0.04 x0.40 should be less than Eth.

The sum of electromagnetic transverse energy of the crystals lying in a cone of ΔR = 0.4, centered around the super-cluster with a veto cone (ΔRi = 3.5 crystals) and eta-slice (Δη = 2.5 crystals) should be less than the threshold value.

IsoHCAL : The sum of hadronic transverse energy of all the particles in the HCAL towers in a hollow cone with an inner radius of ΔRi = 0.15 and an outer radius of ΔRo = 0.4 centered around the super-cluster should be less than a threshold value.

IsoTrk : The sum of transverse momenta of all the tracks in a full cone (ΔR = 0.4) centered around line joining the primary vertex to the cluster should be less than a threshold value.

H/E : - The fraction of hadronic energy to the total electromagnetic energy inside a cone of ΔR = 0.05.

- Low for photon, while high for jets as they carry both electromagnetic and hadronic energy.

Σiηiη : - The transverse shape of the electromagnetic cluster.

- Trajectory of a photon in η is not affected by magnetic field, so its magnitude in η should be small, while for π0 it will tend to be larer

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Photon Isolation Variables cntd..Photon Isolation Variables cntd..

d.) shower shape e.) H/E

Barrel

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