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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 1 Testbeam results of the CMS electromagnetic calorimeter Alessio Ghezzi on behalf of CMS ECAL Collaboration

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 2 Outline Energy reconstruction technique and performances Impact point reconstruction Intercalibration Irradiation monitoring performances Cooling system

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 3 Experimental setup SupermoduleMovable Table Beam Hodoscopes Laser monitoring system and HV system (for APDS) : final scheme LV system : prototype cooling system: final prototype moving table plastic scintillator for trigger Hodoscopes ( ~145 m) Laser monitoring system

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 4 Test beams data 2002 : 100 channels with old electronic (FPPA) detailed study of: Laser monitoring intercalibration cooling system 2003: 2 test periods Electron energies (GeV) 20, 35, 50, 80, 120, 150, 180, 200 25, 50, 70, 100 SM (# equip. crys.) FPPA (100 chan.) MGPA (50 chan.) SM0 SM1 # gains 4 3 period long 1.5 months short 10 days

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 5 Energy reconstruction 3 pedestal samples and 11 signal samples 40 MHz Amplitude T max T pea k Time (*25 ns) SM0/FPPA Under the constraints W i determined minimizing

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 6 Energy resolution Electrons incident on a 4x4 mm 2 central region Pedestal run Amplitude (MeV) : 129 MeV Sum over 3x3 matrix Noise term determined from pedestal runs E /E (%) E beam (GeV)

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 7 Position reconstruction Deposited energy Impact point reconstructed by hodoscopes ( ~ 150 m) Measure impact position from calorimetric information X i : position of the i-th crystal Two methods :

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 8 Position reconstruction Y (reco.–true) mm S curve is E, dependent Resolution varies with impact position (better resolution close to crystal edges) = 700 m Y (reco.–true) mm Logarithmic weights G. Daskalakis I. Van Vulpen 1mm

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 9 Intercalibration Procedure selections: e - impacting within a 7 x 7 mm 2 central region ( retains ~25% of events ) Cancel out the dependence of reconstructed energy on impact position by equalizing to the maximum response: IV order polynomial fit M Relative calibration: Channel response: position of peak M, fitted by a Gaussian + exp left tail

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 10 Intercalibration Comparison of intercalibration from different data set Same accuracy as 2002 results Statistical accuracy: compare the intercalibration obtained using only a reduced sample of data w.r.t. to the one with the whole statistic An accuracy of ~ 0.1% can be achieved with 1000 triggered events RMS :~0.3% intercalib. ~1000 triggered events RMS:~0.09% intercalib.

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 11 Intercalibration from laboratory measurements Only few modules will be calibrated on a beam Precalibration starting from Light Yield measurements in laboratory : 60 Co source 1.2 MeV Containment: ~0.8 @ 120 GeV APD Gain Electronic gain M = 4.05% F. Cavallari

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 12 Irradiation Monitoring Laser signal Electron signal = 1.55 ~5% Irradiation affects only the light transmission Monitoring and correct for the loss in response by the injection of laser light as reference A. Van Lysebetten P. Verrecchia

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 13 Irradiation Monitoring / = 6.3% / = 6.3% 2002 and 2003 data: it is possible to use the same for all the crystal After the correction for loss in transparency 2002 A. Van Lysebetten P. Verrecchia Time (hours) signal amplitude (ADC counts) PRELIMINARY

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 14 Thermal step The APD gain (M) depends on the temperature : Also the LY depends on the temperature Average thermistor temperature T = - 4.1 % / °C The two effects sum up in the overall response (R): and measured in a thermal step Laser runs Electrons runs T = - 2.44 % / °C 1 ºC

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 15 Cooling system 1 C 0.1 C 7 days Cooling system with cooling bar ~1.5 month Cooling bars PRELIMINARY

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 16 Summary The new Very Front End cards equipped with MGPA satisfy the target specifications. The impact point reconstruction shows a resolution better than 1mm for Energy > 35 GeV A robust intercalibration procedure on e- beam has been developed, and an initial intercalibration at ~4% level is reachable for all the crystals from laboratory measurements of the light yield The laser monitoring system and the cooling system satisfy the performances required for CMS

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 17 Back up

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 18 Energy reconstruction A pure signal f(t)

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 19 Energy reconstruction (E)/E (%) SM0/FPPA E resolution VS # of pulse samples Normalised T max 25 ns Number of events Spread in Time of maximum response Resolution versus mismatch T max mismatch (ns) (E)/E (%) SM0/FPPA

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 20 Position reconstruction =620 m Y (reco.–true) mm uncorrected S-curve Worst resolution: max. energy fraction in central crystal Best resolution: corrected S-curve Reconstructed (Y) mm close to crystal edge Resolution versus impact position Y (reco.–true) mm E = 120 GeV

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 21 Laboratory measurements Precalibration starting from LY measurements in laboratory : 60 Co source 1.2 MeV

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 22 Test beam 2002 LY 0.5 % LY intercalibration coeff.

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INFN Milano, Universita` degli Studi Milano Bicocca Siena IPRD04 23-26 May 2004 23 Test beam 2002 Cooling average thermistors temperature 2 months 0.06 ºC 2002 Stability over a long period Uniformity of temperature within a module 6 days 0.04 ºC

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