# Presentation: 196438

## Update On Jet Energy Corrections

**Robert M. Harris**
**Fermilab**
**Physics / Trigger Week**
**October 26, 2007**

## Outline

- MC Jet Correction
- Factorization Plan and Status
- Developments in Factorized Corrections
- Zero Suppression Correction
- Response vs. PT for + jet events.
- Jet Correction Methodologies
- Developments in Monolithic Corrections
- Quark Jet Correction Studies
- Global Fit Investigation
- Conclusions

**Discussing status **
**and all updates**
**shown to JetMET**
**And JESTF since **
**September 15-21**
**CMS Week**
**For discussion of**
**developments in **
**the top quark group**
**please see talk by **
**J. D’Hondt**
**yesterday and **
**CMS-AN 2007 / 029**

- Robert Harris, Fermilab

## MC Jet Corrections for CMSSW_1_5_2Kostas Kousouris (JetMET Meet Oct. 4)

- Standard corrections from MC truth released October 6
- For Midpoint Cone R=0.5, 0.7, Iterative Cone R=0.5, 0.7, KT D=0.6
- Official support expected soon for KT  D=0.4, Seedless Cone R=0.5, 0.7
- Un-official version of these corrections have been supplied to the experts.
- Similar correction as Spring07 in barrel and endcap
- Smaller correction than Spring07 in forward which has improved response.
- Asymmetric HF response vs.  at low PT is not corrected.

- Robert Harris, Fermilab

## Factorization Plan

- Factorized jet corrections will replace MC Jet Corrections in CMSSW

- Breaks correction into natural pieces.
- Found in stages of time & precision
-  A. MC truth (now)
-  B. Data-driven techniques using MC (soon)
-  C. Data-driven using actual in-situ data (’08)
-  D. Eventually back to MC tuned on data.
- Factorized corrections are work of the Jet Energy Scale Task Force in JetMET
- Especially the hard working postdocs !

_**Postdocs in JES Task Force**_
**Jochen Cammin (Rochester)**
**L5 Flavour Corrections**
**Selda Esen (Brown)**
**L4 EMF Corrections**
**Kostas Kousouris (Fermilab)**
**L2 ******** & L3 P****T**** corrections**

- Robert Harris, Fermilab

## Factorization Status

- L1 (offset): 1st pass Zero Suppression correction done including code to use it.
- Need pile-up component of correction next.
- L2 (): MC truth  dependence correction almost done.
- No correction code yet.
- 1st study of dijet balance for **data-driven** phase of correction done.
- L3 (pT): MC truth pT dependence correction almost done.
- No correction code yet.
- Study of  + jet balance for **data-driven** phase of correction begun.
- L4 (EMF): MC truth EMF dependence factorization almost done
- Study showing feasibility for limited range of pT and  completed, and work ongoing.
- L5 (flavour): MC truth flavour dependence study ongoing.
- L6 (UE): No developments
- L7 (parton): No developments but we have a volunteer.

- Robert Harris, Fermilab

## Zero Suppression Correction Olga Kodolova (JetMET meet Oct. 4)

- Adds back jet energy lost due to calorimeter thresholds that suppress noise
- Significant correction: 25% for 20 GeV CaloJet in Barrel
- Correction decreases with ET, and has complex  dependence ( ↑ <2, ↓ >2)
- Correction restores jets to there measured vales w/o thresholds.
- 1st Zero Suppression Correction completed and available now in CMSSW
- Special CMSSW_1_3_4 sample w/o HCAL cell level ZSP or Ecal Selective Readout.

**Fractional Correction vs. E****T**** and******

**Jet Response & Closure Test vs. E****T**

**Jets Before Corrections**

**Jets After Corrections**
**= Jets w/o Thresholds**

- Robert Harris, Fermilab

##  Jet Response vs. PT from  + Jet EventsAnwar Bhatti (JES Task Force Oct. 2)

-  + Jet PT balance or MPF provide jet response vs. PT in barrel
- High rate calibration process, but lots of subtle issues need study.
- MPF response a little higher than PT bal. at most PT (radiation?).
- Response to GenJet a little larger than PT bal. (particle vs. parton ?).
- PT bal. response a little higher than dijet system response (q vs. g?).
- Also prior work by O. Kodolova et al and J. Cammin

**Photon P****T**** (GeV)**

**Photon P****T**** (GeV)**

**Jet Response**

**Jet Response**

****

**Jet**

- Robert Harris, Fermilab

## Jet Correction MethodologiesKostas Kousouris (JetMET Oct. 18)

- Four methodologies explored for finding correction vs. pT in barrel.
- Binning in **GenJet** or **CaloJet** pT, measuring response with **ratio** or **difference**.
- Using QCD sample w/o weights (“flat” spectrum) and with weights (QCD spectrum).
**“****MC Jet Method”**: bin in **GenJet** pT and measure **CaloJet p****T**** / GenJet p****T**
- Answers “What is response of GenJet?” independent of input spectrum.
**“****CaloJet Method”**: bin in **CaloJet** pT and measure **CaloJet p****T ****- GenJet p****T**
- Answers “What GenJet pT gave my CaloJet pT?” which depends on input spectrum.
- CaloJet method closes better vs corrected CaloJet pT.
- Similar to work of S. Esen, G. Landsberg and P. Schieferdecker.  Discussion ongoing.

**CaloJet**
** ****Method**

**MC Jet **
**Method**

- No
- Weights

**Spectrum Dependence**

**Correction from Methods**

**CaloJet**
** ****Method**

**MC Jet **
**Method**

- No
- Weights

**Correction**

**Correction**

**CaloJet P****T**** (GeV)**

**CaloJet P****T**** (GeV)**

**Corrected CaloJet P****T**** (GeV)**

**CaloJet Closure Test**

- Robert Harris, Fermilab

## Quark Jet Correction Studies

- Quark jet corrections
-      _Loïc Quertenmont_, Dorian Kcira, Giacomo Bruno (JetMET Oct. 4)
- MC Jet overcorrects W from top
- Because MC Jet  for mixture of q + g ?
- Because of closure issues in MC jet ?
- Quark jet correction found from Z sample
- Private monolithic correction.
- Reconstructs correct W mass.

**No**
**Corr.**

**MC Jet**
**Corr.**

**Quark**
**Jet**
**Corr.**

-  + jet corrections applied to qqH
-      _Efe Yazgan_ and Alexandre Nikitenko (JetMET Oct. 4)
- Jet corrections derived from  + jet sample in CMSSW ala ORCA method.
- Overcorrects qqH jets at high  because of large amounts of gluons at high  in the  + jet sample.

**MC Jet Corr.**

****** ****+ Jet Corr****.**

**No Corr.**

**Maiko Takahashi**

- Robert Harris, Fermilab

## Global Fit for Hcal/Jet CalibrationChristian Autermann (JetMET Oct. 18)

- Trial exploration of framework to combine all factors and perform global fit.
- Work of C. Autermann, C. Sander, P. Schleper, H. Stadie, R. Wolf at Hamburg.
- Test of the tools: calibration of jets and of all 2048 CaloTowers.
- Use + jet sample and form 2
- Between the  energy and corrected jet energy in 110K  back-to-back clean events.
- Between the track momentum and corrected tower energy in 1.5K g+jet events
- Minimize the 2 to find the correction function for each CaloTower and Jet.

**Tower K-factor per event**

**Jet Response**

**Jet Resolution**

- Robert Harris, Fermilab

## Summary & Note

- MC Jet corrections available for 1_5_2
- Factorized corrections will replace it soon.
- 1st Zero Suppression correction available.
- + jet studies begun for correction vs. jet pT in barrel.
- Jet correction methodologies for the factorized correction being actively studied and discussed
- Work on monolithic corrections continues to teach us valuable lessons.
- We are working on completing a draft of our JES note for December CMS week.
- 90% done: 28 pages, 24 plots.
- Needs little more work and editing.

- Robert Harris, Fermilab