Update ON the Study of Subjet Multiplicity at CMS 7TeV

Manuk Zubin Mehta , Manjit Kaur Panjab University, Chandigarh

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Introduction

The jet shape study could provide the tool for quark-gluon jets separation:

• The internal structure of a jet is expected to depend on the type of parton creating the jet (quark or gluon) and ET of the jet.

• the study of jet shapes can help to test the models of underlying events .

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SubJets

*Subjets are defined by reapplying the KT algorithm, this time starting with a constituents of a jet.

*Number of Subjets within the jet is the Subjet multiplicity M.

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Standard Event Selection For Data• Single Jet Trigger HLT_Jet30U •Scraping veto• Primary vertex:

– >= 4 DOF– |z| < 15 cm

• Working in CMSSW_3_8_4 With PAT

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Jet Selection Criteria • Selecting Di Jet (Leading in ET)• Jet Quality Criteria :: Loose Jet ID criteria(EMF > 0.01, n 90

hits > 1, fHPD< 0.98)• |𝜟𝝓 – ℿ | < 1.0• pT > 50 GeV• |y | < 3.00 • KT ,D=0.6 algorithm used

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Data Samples

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Runs 132440-141899/JetMETTau/Run2010A-Sep17ReReco_v2/RECORuns 141900-144114/JetMET/Run2010A-Sep17ReReco_v2/RECO

Runs 144115-149711/Jet/Run2010B-PromptReco-v2/RECO

MC Samples /QCD_Pt30/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO

/QCD_Pt30-herwig/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO

/QCD_Pt30-herwigjimmy/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO

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Monte Carlo used: Herwig++, Pythia 6,Herwig6+Jimmy

• Herwig and Pythia use different hadronization model

•Also using different Underlying Event models(UE is used to tune MC generators to data and measured in transverse region)

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Standard kinematic comparison plots for 3pb -1

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Subjet Multiplicity

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Subjet Multiplicity in various rapidity bins

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Subjet Multiplicity in two different pT bins

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Gluon Jets

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Quark Jets

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Worked in the Pre-Assembly jobs for RPC at BARC

• Gas Blocks and Thermo formable gas pipes.• Ground Cables• Twisted Pair Cables• Mylar sheet cutting

Note: All the things has been prepared for 100 chambers

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Plan of the near future

• We have started evaluating all associated systematic uncertainties .

• Also evaluating multiple (prescaled) trigger streams.

•Also Working on method to find quark and gluon fractions from data.

• Documenting Analysis Note CMS AN AN-10-252.

Comments and suggestions are welcome!

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Back Up Slide

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Subjet Definition

• Using Kt AlgorithmFor every object i, dii = pTi

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For pair(i,j), dij = min (pTi2,pTj

2) R𝜟 ij2/D2

•Find dmin

•For Subjets ::: dmin > dcut

dcut = ycut *pT2(jet)

where 0≤ycut≤1

We have taken (resolution parameter )ycut = 10 -3 for our analysis. Ref::

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