# Difference: JetCalibrationTTBarEvents (2 vs. 3)

#### Revision 32010-01-21 - AndreaMassironi

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 META TOPICPARENT name="AndreaMassironi"

# Jets calibration using events

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http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/Bicocca/HiggsAnalysis/TTBarAnalysis/

## How

Changed:
<
<
How to prepare the environment for the analysis
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How to prepare the environment for the analysis:

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cmsrel CMSSW_3_3_4
cd CMSSW_3_3_4/src/
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cd HiggsAnalysis/TTBarAnalysis scramv1 b
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## Results

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with = / and = /

• MiB : Minuit Bare minimization
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• SFit: Squared Fit
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Occupancy plot
pT Reco / pT MC before jet corrections. Gauss fit mean superimposed.
pT Reco / pT MC before jet corrections.
Reco invariant mass before jet corrections vs η.
Reco invariant mass before jet corrections vs pT.

##### MiB : Minuit Bare minimization
Minimization in space of the function
assuming massless jets, using TMinuit package.

Result: still invariant mass underestimation!

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs η.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### kUpdate
Analytic minimization of . Result:
No iterative method: just one step!

Result: invariant mass overestimation!

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### RUL3 : Random Update L3
As L3 method
but with random update that is: after analysing all the events, not every k is update but only a random sample (tipically one half of the k space). This method is intrinsically iterative, that is many k updates are required.

Why random update? L3 method works fine for "intercalbrations", that is the mean value of k is 1. For jet corrections that is not the truth, then, if for example every k should be about 2, we have about 4 ( is proportional to ) and if every k is updated then the mass will be overestimated by a factor 4, and so on, jumping around the right mass but never approaching it.

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### SL3: Squared L3
As L3 method, but with the ratio of the masses instead of the squared ratio
then the "dimension" of the correction is proportional to k and convergence is reached.

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### RUFit : Random Update Fit
Fitting the invariant mass spectrum for a fixed k, that if filling an invariant mass spectrum for all jet pairs where at least one of the two jet is in the selected bin in k space, and imposing the invariant mass peak to be the right one
but with random update that is: after analysing all the events, not every k is update but only a random sample (tipically one half of the k space), see RUL3 for details. This method is intrinsically iterative, that is many k updates are required to k values to converge.

Result: not performing!

##### SFit: Squared Fit
Fitting the invariant mass spectrum for a fixed k, that if filling an invariant mass spectrum for all jet pairs where at least one of the two jet is in the selected bin in k space, and imposing the invariant mass peak to be the right one
This method is iterative, that is many k updates are required to k values to converge.

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### SL3: Squared L3
As L3 method, but with the ratio of the masses instead of the squared ratio
then the "dimension" of the correction is proportional to k and convergence is reached.

pT Reco / pT MC vs η. Gauss fit mean superimposed.
pT Reco / pT MC vs pT Reco.
Reco invariant mass vs pT.
Reco invariant mass. Red = before jet corrections, Green = after jet corrections

##### Summary
Algorithm pT Reco / pT MC vs pT Reco pT Reco / pT MC vs η Invariant Mass vs pT Reco Invariant Mass
MiB
kUpdate
RUL3
SL3
SFit

### Jet from W identification in events

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