1. 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

2. 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

3. 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

4. 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

5. 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

6. 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)

7. 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 :

8. 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

9. 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

10. 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.

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

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

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

19. 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

20. 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

21. 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

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

23. 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