Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Ecal calibration using 0

Sabine Elles/ Marie-Noëlle Minard/ Gaël Rospabé

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Outline Sample

0 method

De-calibration

Re-calibration

Results

Perspectives

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Sample MinBias 106 evts

Cf talk in december and next one : fisher for Ecal in stand alone

Cuts : Pt > 0.3GeV

Fisher (stand alone) > 0.15 => eliminate non photon clusters

Dist 1 2 < 500mm => eliminate bad combinatories

Gives ~1.80/100events

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Cut effectsEff = 80%

Rej = 50%Eff = 65%

Rej = 80%

Dist < 500mm

Eff = 90%

Rej = 95%

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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SampleNo corrections :

-Shifted mass (124.6MeV)

- large sigma (11MeV)

- because no corrections applied

- 1.8 0/100evts

- S/B = 3

Applying corrections : Mass : 133.2MeV

= 9MeV

With the L0 :

- get 0.3/100evts

- S/B = 3

=> No need to apply it

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Calibration methodBased on the disintegration 0->

Clusters :

2E1E2(1-cos12) = m20E1and E2 deposited energy for each photon 12 angle between the 2

Most energetic cell into the

cluster ( = seed)

Because can bring bias

(correlation between two corrections)

In practice :i = index for cells into the clusterci= calibration coefficientei = deposited energy

E1(2)= Ci,1(2)ei,1(2)

2E1E2(1-cos) = m2 (correction) = m / m0

Cn+1 = Cn *correctioni,1(2) i,1(2)

Where n is the iteration index

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Biases come from : cells shared by several clusters clusters between two regions of the Ecal extended clusters

Solutions : adding others selections only clusters with more than 70% of total energy

into the seed applying energy corrections only to the seed and

taking into account other corrections on other cells 0.1< 0 mass < 0.17GeV : less than 20% of error

=> 10/100events

Calibration selections

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Effects of the cuts on the clusters

Cuts on Pt > (0.3GeV), Fisher (> 0.15), Dist 1 2 < 500mm and % of total energy into the seed make us keeping compact clusters

Without cuts

Pt, dist, fisher cuts+ seed cut

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Calibration Algorithm

• Cells grouped in 3x3 patterns for each region

• 9 random numbers for each region (vs Gaussian)

• Patterns reproduced along x & y axis

• cells de-calibrated in function of position in 3x3 patterns

• 2 consecutive cells with de-calibration coefficients

• seed coefs only changed : no bias and correlations

• decalibration level can be chosen

Detector de-calibration :

Method : getting closer from “reality” (realistic data tacking and first mis-calibration) : de-calibration / re-calibration

Outer

Middle

Inner

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Outer region

Inner regionMiddle region

De-calibrationIn each region : 9 coefficients => 9 distributions

In total : mean=120MeV = 26MeV(red =initial distributions)

m=120MeV = 26MeV

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Calibration algorithm

Detector calibration :

Different parameter evolutions are checked : mean (mass), sigma of mass distributions, and dispersions for each region when for a given region stop criteria (see next transparencies) are satisfied : stop to re-calibrate this region and only going on for non-re-calibrated ones

Distribution of calibration coefs :9 distributions /

region

Nowadays: - a 0 is randomly selected into the sample- fill the dedicated histogram (position into the 3x3 pattern) with it’s reconstructed mass - when one contains 1000 0 : Gaussian fit => gives mean value : m which is m2 = 2E1E2(1-cos12) - correction is calculated :

- the correction is applied giving 2E’1E’2(1-cos) closer to m2

0mm =

0

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Coefficient re-adjustment9 examples of distributions of the mean :- not very Gaussian- not centered on m- distributions fitted by a Gaussian- give us the correction to apply on the cell(s)

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

13Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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How to stop/evolution of the calibration3 variables to check :

- evolution of the mean of the distributions

- the of the distribution- the dispersion

Dispersion (Disp) is defined by :

Disp = (mean – mbin )2 x Bin content

Stop iterative process for one region when system stables over 4 quantities (0.1%) :

-Correction factors

- mean,

and dispersion

for global distribution and for each region

bin

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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How to stop/evolution of the calibrationOscillations of the mean :

- over-corrected

- corrected

Diminution of the mean and dispersion

Inner oscillates more than other regions

Middle stabilizes faster than others

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Results for the total Ecalm=135 MeV = 9 MeV

mi = 120MeV

Even if it looks well calibrated before the end it is not !! Because of the addition of the 3 regions

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Results for the total Ecalm=135 MeV = 10 MeV

m=135 MeV = 8 MeV

m=135 MeV = 11 MeV

Gael Rospabe Lapp 15/04/08 CaloSoft Meeting

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Conclusions Iterative method : correction of the mass obtain resolution of 1% on each cell Time 1753 seconds (~1/2h) CPU 290.17 seconds (~5mins)*2000/9=18h Number of iterations : ~200 # of needed 0 = 1000/cell => ~1070

with Fisher and selections 1.0/100evts =>

3.108evts Calibration time and iterations function of de-

calibration