An ATHENA package for

jet performance studies

V. Giangiobbe	(INFN-Pisa)

K. Lohwasser	(University of Oxford)

First Annual ARTEMIS Meeting, 27-28 September 2007-	THESSALONIKI

Provide a reproducible set of plots to check the performance of the jet calibration algorithm

follow evolution of the performances

compare/validate new calibration strategies with existing ones

Athena package

configurable with jobOptions

can be installed in a standard way

Provide plots for the CSC ATLAS note

Main purposes of a Jet Performance Package

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Jet collections

Jets built from Tower and Topological clusters,

Clustering with cone 0.4 and cone 0.7

Calibration with H1 method

Linearity and energy resolution vs E

vs Energy	: central region (0.2 <||< 0.4) and forward region (2.35 <||< 2.55)

vs 	: 30 < ET < 40 GeV and 480 < ET < 640 GeV

Spatial resolution vs 

(rec)-(truth) and (rec)-(ruth) for 30 <ET< 40 GeV and 480 <ET< 640 GeV

Efficiency and purity vs ET and  of the truth jet

3 eta regions	: 0 <||< 0.5; 1.7 < || <2.5; 3.7< || <4.2

2 ET regions	:	30< ET<40 GeV; 480 < ET < 640 GeV

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Requested plots for ATLAS Detector Paper

JetPerformance.cxx

JetPerformancePlots.cxx

Intermediate root file

for crosschecks, debugging, dedicated analysis

AOD/ESD files

Calibrated jets

MC jets

Performance plots

root, gif, eps format

step 1

step 2

CVS : Reconstruction/Jet/JetPerformance

Data set used so far

Official QCD dijet samples

Misaligned geometry with material distortion

Structure of the Jet Performance algorithm

(still under development)

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General structure of the JetPerformance package

Input file : AOD/ESD files containg jet collections (reco jets, MC jets)

Performs the matching between MC jets and reconstructed jets

matching cone ∆R, set in jobOptions file

For each bin (in , , ET or E) save 1-D and 2-D histograms

EReco/ETruth (if ETTruth > TrueJetCut and ETReco > RecoJetCut )

Reco- Truth (same cuts on ET)

Reco- Truth (same cuts on ET)

Number of true jets vs ET and eta (no cuts on ET )

Number of reconstructed vs ET and eta (no cuts on ET )

Number of true matched jets vs ET and eta (no cuts on ET )

Number of reconstructed jets vs ET and eta (no cuts on ET )

Output file : ROOT histogram file

The JetPerformance algorithm

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For each jet collection the following info is available :

Backup of the histograms conditions

matching cone, ETtruth cut, ETreco cut

Number of Energy, Eta, Phi bins

Size of the bining in E, Eta, Phi

...

Histograms (1D, 2D)

E(rec)/E(truth) for each bin

Spatial resolution in eta for each bin

Spatial resolution in phi for each bin

Number of MC Jets vs ET and eta

Number of reconstructed Jets vs Et and eta

Number of matched MC Jets vs Et and eta

Number of matched MC Jets vs Et and eta

The intermediate output root file : structure

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Distribution of EReco/ETruth

Distribution of Reco- Truth

Distribution of Reco- Truth

The intermediate output root file : example

For 0 < Truth< 0.5 and 75 < ETruth< 90 GeV

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Linearity and resolution

For each bin in //ET/E, fit E(Reco)/E(Truth) distributions with a Gaussian function (± 2 range) ⇒ get  and 

Linearity : Plot  vs E(Truth) and 

Energy resolution : Plot / vs E(Truth) and  + fit with 2 or 3 parameters :

Spatial resolution : For each bin in  fit (Reco)-(Truth) and (Reco)-(Truth) distributions with a Gaussian (± 2 range) ⇒

Efficiency

Plot (Number of matched reco jets) / (Number of reco jets)

Purity

Plot (Number of matched true jets) / (Number of true jets)

Drawing performance plots

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E(rec)/E(truth) vs E(truth)

(rec)/E(rec) vs E(truth)

E(rec)/E(truth) vs (truth)

(rec)/E(rec) vs (truth)

Some example plots : linearity and energy resolution

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Resolution ~8% at 100 GeV in central region

(rec)-(truth) vs (truth)

(rec)-(truth) vs (truth)

Some example plots : spatial resolution

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Some example plots : Efficiency & purity vs eta

efficiency

Nb matched true jets / Nb true jets

purity

Nb matched reco jets / Nb reco jets

30 < ET(truth) < 40 GeV

480 < ET(truth) < 640 GeV

30 < ET(truth) < 40 GeV

480 < ET(truth) < 640 GeV

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Some example plots : Efficiency & purity vs E(truth)

0 < |  (truth) | < 0.5

3.7 < |  (truth) | < 4.2

0 < |  (truth) | < 0.5

3.7 < |  (truth) | < 4.2

efficiency

Nb matched true jets / Nb true jets

purity

Nb matched reco jets / Nb reco jets

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Official Jet Performance package under development

meant to be easy and flexible to use

still some efforts to make it conform to ATHENA coding rules

will be soon put into release 13.X.X

First plots for the ATLAS CSC note have been provided using this tool

Any suggestion for improvment are welcome

Conclusions...

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W(Jet Energy) x Sample energy

W(Cell Energy density) x Cell energy

W(Cell Energy, Jet Energy) x Cell energy

Backup : calibration methods

Use global jet scale, See A.Dotti presentation, (Pisa groups)

Default in Athena, used in all physics analysis up to now and for ETMiss. Indicated with H1 (F.Paige)

Simple and fast but less performant, useable at trigger level ? (A.Gupta)

All weights are also function of eta.

Different functions are assumed to describe the weight energy dependence.

Energy resolution minimization (with linearity constraint) to obtain weights W() :

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2007-09-10T09:58:20