Jets and Missing Et - home.fnal.govhome.fnal.gov/~bhatti/doe/doe06/doe06_cms.pdf · Jets and...

Jets and Missing Et

Anwar A BhattiNovember 28, 2006

DOE Site Visit

November 28, 2006 Anwar Bhatti DOE Review 2

Jets at LHC/CMS

Good understanding of jets/Missing Et are needed for

a) SM confirmation (i.e. detector is working)b) Higgs Mass reconstruction (MSSM )c) SUSYd) Higgs search (H WW lνlν, H ZZ llνν) e) High mass Higgs boson, new particles, Quark Compositeness …f) Reject Standard Model BackgroundGood understanding of hadron calorimeter needed for lepton identification also.


The CMS Calorimeter

EM calorimeter |η| < 3 :PbW04 crystals1 longitudinal section/preshower 1.1 λ∆η×∆ϕ = 0.0174 × 0.0174Central Hadronic |η| < 1.7 :Brass/scintillator +WLS2 + 1 Hadronic Outer – long. sections 5.9 + 3.9 λ (|η| =0) ∆η×∆ϕ = 0.087 × 0.087Endcap Hadronic 1.3< |η| < 3 :Brass/scintillator +WLS2 or 3 longitudinal sections 10λ∆η×∆ϕ = ~0.15 × 0.17Forward 2.9 < η < 5:Fe/quartz fibers ∆η×∆ϕ = ~0.175× 0.17

Hcal barrel and EndCap

EM barrel and EndCap

Very Forward Calorimeter

Hadronic Outer

Towers of dimension ∆η×∆ϕ = 0.087 ×0.087 gradually increasing in endcap and forward regions are formed for a total of 4176 tower.


Jet Reconstruction and Validation

Jet clustering algorithms Calorimeter noise and its effect on jet clustering.Un-clustered energy in the Midpoint Clustering Algorithm(Husseyin Topakli, Cukurova U., Adana, Turkey).

Jet software validationSoftware to validate every release of software with Robert Harris (Fermilab), Fedor Rantikov (Maryland).Many checks for initial performance of jet software.


Noise in Central Calorimeter in cone of R=0.5

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nConeTower00 nConeTower00Entries 5400Mean 27.16RMS 4.584Underflow 0Overflow 0Integral 5400

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emConeTower00 emConeTower00Entries 5400Mean 1.928RMS 0.4506Underflow 0Overflow 0Integral 5400

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hdConeTower00 hdConeTower00Entries 5400Mean 6.52RMS 1.947Underflow 0Overflow 0Integral 5400

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hdConeTower02

No thesholds<n> = 27<EB> = 1.9 GeV<HB> = 6.5 GeV

EB> 0.15 GeVHB> 0.6 GeV<n> = 4.5<EB>= 0.3 GeV<HB>= 2.2 GeV

EB> 0.18 GeVHB> 0.8 GeV<n> = 2.1<EB>= 0.3 GeV<HB>=0.4 GeV


Noise Suppression

Cell Threshold

Scheme HB GeV HO GeV HE GeV Noise in Cone GeV η= 0

Jet Energy Loss GeV η = 0

A 0.7 0.85 0.9 1.4 -

B 0.9 1.1 1.8 0.3 1.0

C 1.2 1.3 1.8 0.2 1.9

A or B schemes are used for physics studies

HB Hadron BarrelHO Hadron Outer HE Hadron Endcap

JetMET group recommended these thresholds in Physics Technical Design Report Vol. I for all physics analysis.


Fast Calorimeter Simulation (GFlash)

Current Geant4 (G4) calorimeter simulation may not reproduce the test beam data. Implement GFlash which is easily tunable and is quite fast.

GFlash uses parameterized showers. The particles produced in the pp collision are propagated by G4 to the first interaction in the calorimeter. After first interaction, control is passed to GFlash which deposits energy according to tuned parameters.Successfully used by H1 and CDF experiments.

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Longitudinal Profile Barrel_LongitudinalEntries 26Mean x 12.5Mean y 555.4RMS x 7.5RMS y 557.5

Reference

New

PV=1

Longitudinal Profile

•Software for electromagnetic particles written by Joanna Weng.

•Working with Soon Jun (Carnegie Mellon), Romulus Godang (U. Mississippi)to implement for haronically interacting particles and over all tuning.

Comparison of full G4 and GFlashLongitudinal Profile 30 GeV Photons

Depth (X0)


Simulation based on GFlash

Implementation of GFlash in CMSSW.Does GFlash parameterization work for high energy particles? How good GFlash flavor dependence of response is? Compare with G4.Is geometry in CMSSW correct? specially boundaries?Is material in CMSSW correct? How to measure/tune with real data?How to simulate boundaries in GFlash? Do we need special treatment?Measure in G4, parameterize and use Post-GFlash.

How to treat HadronOuter in GFlash? Forward Hadron?How to treat muons in GFlash? do we use G4 for muons?Measure single particle response in G4, transverse profile, E/pTune GFlash to G4 (transverse profile, E/p), build tools.Test Beam analysis, transverse shape, E/pTriggers for single track in collision data, HLT algorithmsSingle track data analysisTuning of GFlash/G4

Anwar A Bhatti LHC Physics Center Fermilab April 19, 2006


Calorimeter Response

Beam momentum [GeV/c]1 10 210

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o /

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om

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2006 Test Beam• Ecal+Hcal test beam in Sept 2006.

• First time full Ecal module tested along with Hcal.

• Good particle identification at low momenta. (problem in 04 Test Beam)

• Hcal analysis mostly done at LPC (daily meeting at 4 pm)

• RU working on measuring transverse profile of hadronicshowers.

• Evaluation of new photo-detectors for HardonOuter calorimeter (muon signal, dynamic range, dead time) Very clean test beam data


LPC Jet Energy Scale and Resolution Group

Informal group, meets every week on Tuesdays Students and post docs from various universityRutgers University (Lalith, Dmitry)University of Illinois at Chicago (Lenny, Agata)University of Rochester (Gennady, Jonathan, Jochen)University of Cukurova, Turkey (Selda, Pelin, Mehmet, Huseyin)


Jet Reconstruction and Jet Corrections

• A calorimeter/particle jet is defined by an algorithm.

• Jet kinematics and corrections depend on the reconstruction algorithm and parameters.

Rec

onst

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ion

Calorimeter jets ↓

Particle jets↓

Parent Parton


Calorimeter Jet to Particle Jet to Parent Parton

Multi-step approach to isolate various detector and physics issues.φ uniformity (material effects?)η uniformity (parton radiation, transverse shower size)Absolute scale for calorimeter response

Simulation based correctionsPhoton-jet balancing (determined directly from data)

Parent parton energy (correct for any radiation outside the clustering cone)Validation of jet energy scale using W JJ in top quark events


Distance of particles from Jet axis(η, φ space) |ηjet|<1.0

Multiplicity

<N>=13.4

<N> 18.8 <N>=26.6

<N>=33.4 <N>=38.9 <N>=44.3

<N>=49.4<N>=60.44

PtJet 10-30 GeV 30-50 GeV 80-120

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800-1000 3000-3500 GeV

Pelin Kurt


Jet Energy Fraction

Photons

Muon/Neutrinos

Neutron/Klong

Charged hadrons


Flavor Composition of a Jet

PtJet 30-50 GeV

Particle ID <N> RMS <PtFraction> RMS

Photon 8.5 3.9 24.8% 15.9%

Neutron/KL 1.3 0.8 7.9% 11.1%

Muon/ν 0.5 0.1 0.3% 0.3%

Charged Hadrons

10.0 3.4 67.9% 17.4%

Large fluctuation between Em <=> Hadronic components combined with calorimeter shower fluctuations makes determintion of jet energy scale difficult.


Jet Response in CSA06 Data Sets

Tune the calorimeter simulation to test beam measurements,

Generate jets using (Pythia) fragmentation model,

Compared calorimeter jet with Particle jet Determine jet corrections

Mehmet Vergili

Many physics data sets were produced as a part of Computing, Software and Analysis (CSA) exercise in Sept-Nov 2006.


Calorimeter-Jet to Particle-Jet Corrections

Initial corrections will be based on simulation.

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PtCalorJet/PtParticleJet

Software to determine the jet response by Rockefeller U.Fitting/parameterization by Moscow State University. Maintenance by Selda/Duong Nguyen Brown University.


Absolute Scale using Photon-Jet balancing

Decouple the jet energy scale between data and MC events.(A short cut: Simulation need not reproduce the data exactly.)Issues

Determine particle jet or parent parton energy. ISR and non-linearity in the calorimeter.Difference in gluon/quark jets.Dijet background (fake photons).

Photon-jet balancing Techniques:Missing Et Projection Method: Use whole event, determine particle-level jet correction, less sensitive to radiation in the event (used by D0). Pt-balance Method: Parent parton energy, less sensitive to low energy calorimeter response. Used by CDF as a cross check. At particle level balance is not 0.


Absolute Energy Scale from the Data

Photon-Jet Balancing


Jochen Cammin

U. Of RochesterPhoton-Jet Balancing

Photon |η| ≤1.0

Pt Jet > 15 GeV

∆φ(γ,jet) > 2.8

Need to study:

Trigger

Isolation criteria

Radiation effects


DiJet Balancing (Rockefeller U., Fermilab responsibilty)

Purpose:Make the detector jet response uniform vs pseudo-rapidity.Advantage:

Jet absolute calibration will need to be done only in a limited region in η.Cross check of the simulated data.

Issues:Only true in 2 2 scattering, Pt1=Pt2 at parton level.Final/initial state radiation spoil the exact balance but the effect should average out.

Reduce ISR/FSR effects: ∆φ> 172 deg, PtJet 3< 20May not be true at particle-level (η dependence in OOC radiation?)Pile-up and underlying event (Low Pt, probably the Pt distribution isuniform in η but calorimeter cares about energy, different point on E/p curve.)Noise contribution (Different in different regions of calorimeter)Different resolution/smearing in different regions of calorimeter.

Needs a detailed study but these effects ~2-3%.


DiJet Response Mehmet Vergili

Particle Jets

Calorimeter Jets

Eta of Probe Jet


Dijet Balance Based Jet Correction

><+><−

MPFMPF

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PhotonJet Response

Absolute scale compared to EM calorimeter scale

CaloJet/ParticleJet


Jet Energy Resolution using Local Clusters

Identify sub-clusters in a jet and correct each cluster based in energy deposition in Em Calorimeter and Had Calorimeter.

Cluster em cells within R=0.03, (3x3 cells)Cluster had cells within R=0.15, (3x3 cells)Match em clusters with had clustersClassify clusters based on had and em energies and transverse shape.Correct hadronic clusters (particle) for difference in ECAL response to hadron and electrons. ECAL is calibrated for electrons.We worked with Lalith in old software framework before he left to work on Forward Pixals. Now working with Turkish students.Add the tracking information later.


e/h corrections to single pions

( / ) ( / ) /[1 ( / ) 1) ]( / ) ( / ) /[1 ( / ) 1) ]

( / ) ( / )

E E E o

H H H o

E E H H

e e h e h fe e h e h f

E e e

ππ

π ε π ε

= + −= + −

= +

f0 =a3log(e_ecal+e_hcal)^a4

is average neutral fraction of shower.

Three param describe e/h of two sections

15 GeV π<E>=15.41 GeV

Five parameters describe the response obtained from to 10, 30, 100 and 300 GeV test beam data.

15 GeV pions

After correctionsBefore corrections

Dan Green 2004 Test Beam

Energy deposition by early and late showers is different. One can improve resolution if energies in Em and Had calorimeters are corrected separately.


Towers in a QCD events Husyein Topakli

Towers 358

Em/Etot

Et of towers

QCD jet events 80-120 GeV

57 towers inside jets with Pt>10 GeV.

Use CaloTowers, order in Et and

Cluster towers in R=0.15 (3x3)

Working on clustering from RecHits


Local Clusters from Towers

Number of Clusters

Towers in Clusters

Et of Clusters

Em/Etot<Towers/Cluster>=1.14

<Cluster>=313.6


SumEt/Met from Clusters Before and After Corrections

From Clusters After Corrections

Before

After

Need to implement cluster corrections derived from the simulation.

Missing EtSumEt MissingEtSignificance


CDF4CMS

Missing Et Startup workshop Sept 22, 2006CDF experience in monitoring the calorimeter stability (Anwar)

Jet Workshop (Dec 14-15, 2006)CDF Experience with jets reconstruction, jet energy scale and jet resolution (Kenichi Hatakeyama).

FP420/TotemBackground studies, alignment issues, exclusive jet analysis.


Missing Et in Inclusive SUSY Events at CMS

Inclusive SUSY Production in mSUGRASUSY Low Mass Point 1 (consistent with WMAP data)Dominated by gluino and squark production σ(LO)=49 pbMgluino= 611 GeV and msquark ~ 520, tanβ =10Cascade decays lead to final state containing

two stable neutralinos (=LSP) → Missing Et.

Koji Terashi

(GeV/c)T

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Correct Generator METCalorimeter RawCalorimeter Corrected (Type 1)

Missing Transverse Momentum

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9860 GenJet4329 matched CaloJets

Jet1 Transverse Energy (MidPoint R=0.5)

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Missing Transverse Momentum vs 2-LSP Transverse Momentum


Conclusions

The work on jet energy scale determination is progressing.We are working on test beam data to understand the calorimeter response and shower shapes.Some people have joined the jet energy scale and resolution effort at CMS but we need many more people to complete the job.The work on improving jet energy resolution using local clusters re-started in new software framework. We are working to determine corrections from simulated data instead of test beam data.It will greatly help to have an additional Rockefeller post doc towork on these projects, specially to improve the jet energy resolution. We have started working on SUSY search in Jets+MET channel and missing Et correction issues.We have a nice Rockefeller office at LPC (11th floor Wilson Hall) now.

Looking forward to LHC data to discover physics beyond the Standard Model

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