Stato della Calibrazione EM D.Banfi, L.Carminati, L.Mandelli 30-1-09

Sommario Necessita’ di una calibrazione piu’ raffinata per i fotoni, che distingua fra fotoni convertiti e non convertiti Studiati tre possibili approcci al problema: Peso globale Parametri indipendenti dal raggio di conversione Parametri dipendenti dal raggio di conversione Studio sostanzialmente concluso (solo alcuni dettagli rimangono da discutere) Nota in preparazione sulla calibrazione dei fotoni 30-1-09

Energia depositata davanti al calorimetro Efront Photons E=100GeV 0.7<η<0.9 L’energia depositata davanti al calorimetro varia sensibilmente con il raggio di conversione del fotone not converted all converted Efront Photons E=100GeV 0.7<η<0.9 all converted conv radius (from MC truth) <40cm 40cm < conv radius < 80cm 80cm < conv radius < 120cm 30-1-09

Energia depositata fuori dal cluster Photons E=100GeV 0.7<η<0.9 Anche l’energia depositata fuori dal cluster e’ dipendente dal raggio di conversione del fotone -not converted -all converted all converted conv radius (from MC truth) <40cm 40cm < conv radius < 80cm 80cm < conv radius < 120cm Photons E=100GeV 0.7<η<0.9 30-1-09

Photons 25GeV All photons Unconverted photons Converted photons ΔE = 24.59 - 23.55= 1.04 GeV ΔE = 24.95 – 24.94= 0.01 GeV 30-1-09

Photons 100 GeV All photons Unconverted photons Converted photons ΔE = 99.52 - 98.71 = 0.81 GeV ΔE = 99.97 - 99.75 = 0.22 GeV 30-1-09

Samples and statistics Photons Energy dataset events 10 GeV 007081 ~1.1M/1.2M 25 GeV 007082 50 GeV 007062 75 GeV 007083 ~0.9M/1.2M 100 GeV 007063 200 GeV 007084 500 GeV 007085 ~400K/400k 1 TeV 007086 ~200/200k Tot ~7.0M/7.8M Considering the conversion probability (from 10 to 50% as a function of η) and the IsEm efficiency (from 40 to 90% as function of η and E) we have, in the region with more material in front of calorimeter, less than 1k converted photons for each cell and energy. The parameter dedicated to converted photons are computed cell by cell adding up the events of 3 adjacent cells. For conversion radius studies the statistic from 5 cells is added. All the shown distribution for Ereco refers to the stats of 3 cell, each one calibrated with its own parameters.

Dedicated parameters: η = 0.3 25 GeV Eta = 0.3 Converted photos calibrated with: ‘’Standard’’ parameters (any distintion between conv and unconv) parameters ‘’dedicated’’ to conv 50 GeV Better linearity: 24.524.9 49.649.9 99.6100 Sigma of the fitted gaussian are compatible inside errors 100 GeV

Dedicated parameters: η = 1.1 25 GeV Eta = 1.1 Converted photos calibrated with: ‘’Standard’’ parameters (any distintion between conv and unconv) parameters ‘’dedicated’’ to conv 50 GeV Better linearity: 23.524.7 48.749.9 98.8100 Sigma compatible inside errors 100 GeV

Linearity and resolution: Barrel Region Improved linearity but almost the same resolution Linearity Eta = 0.3 Linearity Resolution Eta = 1.1 Resolution Converted photos calibrated with: Standard parameters Dedicated parameters

Conversion radius dependance: η = 0.3 Conv – no conv radius eta 0.3 25 GeV The conversion radius range (from MC truth) is dived into 4 bins in barrel (020,2040, 4060, 6080 cm) and 3 bins in the EndCaps (08,816,1680 cm): for each bin we compute a set of parameters 50 GeV Eta = 0.3 Converted photons calibrated with parameter dedicated to converted: independent from conversion radius dependent from conversion radius 100 GeV Linearity and sigma are compatible inside the errors. 2-5 % reduction of RMS

Conversion radius dependence: η = 1.1 Conv – no conv radius eta 1.1 25 GeV The parameters for converted photons are computed in 4 different bins of conversion radius. Eta = 1.1 Converted photons calibrated with parameter dedicated to converted: independent from conversion radius dependent from conversion radius 50 GeV Linearity and sigma are compatible inside the errors. The RMS shows ~10% improvement with parameters dependent on conversion radius, due to the better calibration of low energy tails 100 GeV

Conclusions and perspectives Conv – no conv radius eta 1.1 Parameters dedicated to converted photons, independent from cvradius, introduce: improvement in linearity, with respect to the standard parameters, both in Barrel and EndCap Negligible effect on resolution on all the barrel, small improvements in the EndCap (we need to extend the study to all the EndCap cells) Parameters dependent on conversion radius give almost the same performance in term of linearity and resolution that the independent from cvradius ones, but reduce the low energy tails (~10 % of RMS reduction at high eta) in the Barrel. More studies are ongoing in the EndCap region. Possible scenarios, in increasing order of complexity: Overall weigth on energy: Pro: very easy approach Cons: effect only on linearity, we loose partly the meaning of the CalibHits approach Dedicated parameters independent from cvradius Pro: it’s is a “full” CalibHits approach Cons: introduce a degree of complication in the calibration (another set of coefs) Dedicated parameters dependent from cvradius Pro: Better performance in the tail calibrations, almost the same performance of point 2 in term of linearity and resolution Cons: Very difficult to extract, big complication in the calibration code complexity 30-1-09

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