Jet Energy Response from Z->ee+Jets 2012

Rajdeep Mohan Chatterjee

Tata Institute of Fundamental Research

INDIACMS MEETING BARC,Mumbai 3-4 August

Outline

Objective Response Estimators Event selection Samples used for MC and Data Triggers used and prescales Data MC comparison of relevant variables Response summary and comparison with other

channels Conclusion

Objective

We wish to study the Response of jets in the CMS detector.

It is important to study how closely a jet reconstructed using detector information resembles the original parton.

Both theoretical and experimental effects can lead to a mismatch between the reconstructed jet and the original hadron in terms of kinematics.

In order to study jet response we use utilize certain event topologies that involve a well measured object. Eg ү+jet,Z+jet and di-jet events.

Response Estimator(pT Balance

)

Response Estimator (MPF)

Event Selection: WP90 condition

Used GSF electrons for the analysis with pT>20 GeV (to be consistant with

the trigger) and |η|<2.4

https://indico.cern.ch/getFile.py/access?contribId=4&sessionId=1&resId=0&materialId=slides&confId=165069

https://twiki.cern.ch/twiki/bin/viewauth/CMS/VbtfEleID2011

Event Selection: Jets Used the standard PAT jets for this analysis

along with L1Fastjet, L2Relative and L3Absolute corrections.

Also studied the effect of L2L3 residuals on data

Added CHS jets Leading jet considered in 3 eta bins [0-1.3],

[1.3-2.5] and [2.5-5]

Event Selection criteria

Used the 2011 WP90 criteria for selecting good electrons

Cleaned the corrected jet collection by demanding that none of the electrons selected above layed within ΔR=0.5 of a jet.

Select non-zero jet events with the |η(leading jet)| in 3 bins[check previous slide] and |η(other jets)|<5 and leading jet p

T>10 GeV, other jets

pT>10 GeV .

The Z boson was reconstructed out of 2 electrons of opposite sign subject to 70 GeV<Z

mass(reco)<110 GeV with p

T(Z)>30 GeV.

|ΔΦ(leading jet,Z)| > 2.7

The data-MC comparison was performed with events satisfying these conditions.

Samples used for data and MCMC: /DYJetsToLL_M-50_TuneZ2Star_8TeV-madgraph-tarball/Summer12-PU_S7_START52_V9-v2/AODSIM

GlobalTag: MC_SQ_V2.db

cross-section: 2950 pb

Data:

/DoubleElectron/Run2012A-PromptReco-v1/AOD

/DoubleElectron/Run2012B-PromptReco-v1/AOD

GlobalTag: DATA_SQ_V2.db

Total integrated luminosity : 1.571 fbTotal integrated luminosity : 1.571 fb-1-1

JSON file: Cert_190456-194479_8TeV_PromptReco_Collisions12_JSON.txt

Triggers used

Tried to look for events where the following HLT had fired:

HLT_Ele17_CaloIdT_CaloIsoVL_TrkIdVL_TrkIsoVL_Ele8_CaloIdT_CaloIsoVL_TrkIdVL_TrkIsoVL versions 16 and 17

This trigger is unprescaled over 2012A,B

Primary vertex distributionBlack->data Red->Re-weighted MC

Z mass

Z pT

Alpha=pT(jet2)/p

T(Z)

Alpha(zoomed)

Response

MPF

Averages in bins of alpha and Z pT

The basic idea is to obtain the response and MPF for alpha extrapolated to 0 in bins of Z p

T

We choose alpha < 0.3

Z pT

bins ={30,60,90,120,150,400}

We have three eta bins for the leading jet [0-1.3],[1.3-2.5] and [2.5-5]

For each Z pT bin at the above value of the alpha the

mean and rms of the response and MPF were evaluated for the Data/MC ratio .

MPF/Response summary 1

MPF/Response summary 2

MPF/Response summary 3

Comparison with other channels

Conclusion

Results presented for a fixed alpha bin alpha<0.3 and different Z Pt bins

Studied effect of CHS in different bins of the eta of the leading jet. MPF with and without CHS is compatible with each other within statistical errors. A few Z Pt bins seem problematic for the consistency of the CHS and non-CHS Pt Balance values.

Differences with other channels need to be understood.

Future works

In the near future would study response for uncorrected jets as incorporate MET corrections

Other MC generators like Herwig are to be included

We should strive to be unify our event selection with the other channels.

Variation of Response with time needs to be studied

Preliminary results in AN-12-245. Needs to finalized with the updated luminosity.