1. The CMS electromagnetic calorimeter: status, performance with cosmic and first LHC data Cristina Biino* - INFN Torino 11th ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications Villa Olmo, 5 ‐ 9 October, 2009 *On behalf of the CMS Electromagnetic Calorimeter Group Cristina Biino* - INFN Torino 11th ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications Villa Olmo, 5 ‐ 9 October, 2009 *On behalf of the CMS Electromagnetic Calorimeter Group

2. Electromagnetic calorimeter at CMS –System description Results from cosmic ray running –Performances –Response stability Results from LHC beams data Current status Conclusions Outline

3. Pixels Tracker ECAL HCAL Solenoid Muons Benchmark channel: discovery of low mass Higgs in H  channel Target energy resolution 0.5% at high energy for unconverted photons ECAL Barrel ECAL Endcap The CMS detector requirements Scintillating PbWO 4 crystals; Pb/Si preshower E.M. Calorimeters: ECal barrel & endcap Compact & modular Hermetic Large Energy Range Fast & Stable Radiation Resistant Excellent Energy Resolution CMS ECAL statusECAL Detector C. Biino – ICATPP 09

4. Barrel (EB) 36 SuperModules (18 per half barrel) 61,200 crystals Total crystal mass 67.4t |  | < 1.48  x  = 0.0175 x 0.0175 Endcap Preshower (ES) Pb (2X o ) / Si (1X o ) 4 Dees (2 per endcap) 4,300 Si strips 1.8mm x 63mm 1.65< |  | < 2.6 Endcaps (EE) 4 Dees (2 per endcap) 14,648 crystals Total crystal mass 22.9t 1.48< |  | < 3  x  = 0.0175 2 ↔ 0.05 2 Barrel crystals Pb/Si Endcap Preshower Endcap ‘Dee’ with ‘Supercrystals’ ECAL design and layout CMS ECAL statusECAL Detector C. Biino – ICATPP 09 Crystals are projective and positioned pointing slightly off the IP to avoid cracks. Homogenous Lead Tungstate (PbWO 4 ) Crystal Calorimeter & Pb-Si Preshower

5. Challenges: Crystal LY temperature dependence -2.2%/ O C Need excellent thermal stability (±0.05 O C) Formation/decay of colour centres Need precise light monitoring system Low light yield (1.3% NaI) Need photodetectors with gain in magnetic field Properties: Homogeneous medium Fast light emission ~80% in 25 ns Short radiation length X 0 = 0.89 cm Small Molière radius R M = 2.10 cm Emission peak 425nm Reasonable radiation resistance to very high doses Light yield (23cm) 100  /Mev 23cm 25.8Xo 22cm 24.7Xo EB crystal, tapered 34 types, ~(2.6x2.6 cm 2 at rear)x23cm Two avalanche photodiodes (APD), 5x5 mm 2 each, QE ~75%, Temperature coeff.: -2.4%/°C EE crystal, tapered 1 type, (3x3 cm 2 at rear)x22cm Vacuum phototriodes (VPT), more rad hard than diodes; gain 8 -10 (B=3.8T), Q.E. ~20% at 420nm Scintillating crystals and photodetectors PbWO 4 Producers: BTCP (Bogoroditsk, Russia) SIC (Shanghai, China ) CMS ECAL statusECAL Detector C. Biino – ICATPP 09

6. ECAL readout & pulse shape reconstruction VFE card: 3-gain amplification, shaping, digitization & sampling every 25nsec From ten time samples reconstruct the signal amplitude A and T max using digital filtering technique, weights, fit and ratio methods. Subtract the pedestal P on event-to-event digitization via ADC CMS ECAL statusECAL Detector C. Biino – ICATPP 09 Energy resolution goal is 0.5% at high energy Time resolution goal is 0.1 nsec

7. 2007: Individual signoff of each SM during installation in P5; H4 EE Test Beam 200620072008 2006: H4 Test Beam: 9 SM calibrated; H2 Combined Test Beam: ECAL&HCAL 2006-2007: Commissioning & calibration of each SM with cosmics on surface 2006: 2 SM tested with B-field on surface (MTCC) 2008: Endcap Installation; Commissioning with cosmics and first beam in-situ 2009: Installation of Preshower and commissioning of Endcap trigger 2009 Highlights from ECAL project timeline CMS ECAL statusECAL Detector C. Biino – ICATPP 09

8. Toyoko Orimoto, Caltech8 EB Module: 400/500 crystals EB @ P5 EB SM with electronics EE Dee EE Dee 1 & 2 @ P5 SuperCrystal ECAL construction CMS ECAL statusECAL Detector C. Biino – ICATPP 09

9. ECAL barrel installation in 2007 CMS ECAL statusECAL Detector C. Biino – ICATPP 09

10. ECAL Endcaps assembly in 2008 CMS ECAL statusECAL Detector C. Biino – ICATPP 09

11. ECAL Endcaps installation in 2008 CMS ECAL statusECAL Detector C. Biino – ICATPP 09

12. basic cluster super-cluste r Particle energy reconstruction Electrons and Photons are essential in: at least two of the Higgs decay channels decay of a new heavy bosons Supersymmetry Standard electroweak and QCD processes containement correction CMS ECAL Performance ECAL PerfomanceC. Biino – ICATPP 09 Unconverted Photons –Best energy estimate: energy sum in fixed arrays of crystals (  97% of the shower contained in a 5x5 arrays) –Containment corrections (position dependent) precisely measured at test beam with electrons Electrons/Converted Photons –Require recovery of Bremsstrahlung in tracker material (  1 X 0 ) –Super-clusters of clusters along  (bending direction) –In the endcaps, add also the energy deposited in the preshower

13. ECAL energy resolution Nine Barrel SuperModules were studied at test beam with electrons in the energy range 15-230 GeV. Achieved constant term in energy resolution better than 0.5% Noise is at  40 MeV level per channel, as expected. Each Barrel SuperModule was exposed to cosmics for at least one week with increased APD gain.  5M triggers per SM (average of about 500 good events per crystal) (σ/E) 2 = (3.37%/√E) 2 + (108 MeV/E) 2 + (0.25) 2 Only 500 Endcap channels were calibrated with 120 GeV electrons. Light yield measurement for each crystal; photocathode QE, gain and total photo- electron yield measured for each VPT CMS ECAL Performance ECAL PerformanceC. Biino – ICATPP 09

14. Calibration & Monitoring Some Results CMS ECAL Performance ECAL PerfomanceC. Biino – ICATPP 09

15. ECAL Calibration & Monitoring Uncalibrated Supermodule : 13%-25% spread in resolution among channels Lab Pre-Calibration: 4% EB, 10% EE (all crystals) Cosmic Pre-Calibration: 1.5-2.5% (all EB) TestBeam Pre-Calibration: 0.3% (1/4 of EB & 500 EE xtals) In-Situ Physics Calibration: 0.5% resolution Without inter-calibration, same signal would produce different outputs in different crystals. Also need overall energy scale Calibration of ECAL crucial to maintain high energy resolution. ECAL Stability (<< 0.5%): Monitored with Laser System Transparency Change Correction: Signal Change under Irradiation, Measured with Laser Monitoring System ECAL Monitoring (Monitor Stability and Measure Radiation Effects): CMS ECAL Performance ECAL Calibration & MonitoringC. Biino – ICATPP 09

16. ECAL In-Situ Calibration Goal: improve startup calibration as quickly as possible in-situ StrategyTimePrecision  symmetry: use invariance of mean energy deposited by jets at fixed  Few hours~ 2-3%  0  : mass peak @ low luminosity Few days<= 1% Z  ee: absolute energy calibration 100 pb -1 < 1% W  e : E/p measurement 5-10 fb -1 0.5% CMS Preliminary L=2x10 30 cm -2 s -1    CMS Preliminary L=2x10 30 cm -2 s -1 CMS ECAL Performance ECAL Calibration & MonitoringC. Biino – ICATPP 09

17. During LHC cycles the ECAL response will vary, depending on irradiation conditions and crystal characteristics: –Transparency changes and fast recovery (a few hours) Damage and recovery are monitored by laser light injected into each crystal through optical fibres –Blue light (440 nm) tracks response –Infrared (796 nm) provides a check The laser is pulsed during the LHC ‘orbit gaps’ An optical switch directs light to one half-supermodule or one quarter-Dee in turn. A complete cycle takes ~ 20 min. Small transparency changes at start-up ( L = 10 30 –10 31 cm -2 s -1 ) Corrected response Raw response Time (hours) ADC  2 /ndf =73.9/68 Test beam data Simulation of crystal transparency evolution at LHC ( L = 2 x 10 33 cm -2 s -1 ) - based on test beam irradiation results 0.2% Stability of the crystal response Laser monitoring system CMS ECAL Performance ECAL Calibration & MonitoringC. Biino – ICATPP 09

18. Performance with Cosmics Some Results CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09

19. Commissioning ECAL with cosmics CRAFT: Cosmic Run At Four Tesla –continuous running for several weeks to gain operational experience –> 300 M cosmic events collected –magnetic field operated at 3.8T –most of CMS subsystems participating Minimum ionizing particles deposit 250 MeV in ECAL. Increase efficiency: signal/noise enhanced (x4) in EB to the value of 20, by increasing the gain of the APD. CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09

20. ECAL: timing and occupancy SUSY09A. David ϕ E seed > 100 MeV Timing – bottom is late (t.o.f.) Occupancy – top is busier (shaft side) Top Bottom 20 CRAFT CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09 (25 nsec units)

21. 3x3 crystal energy deposit confirms absolute energy scale to few % MeV 3x3 crystal energy deposit confirms absolute energy scale to few % MeV Energy deposits per ECAL cluster from cosmics. Depend on track length inside the active ECAl volume Cosmic rays CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09

22. Validate ECAL calibration with muons: measure energy deposition vs muon momentum ECAL stopping power Collision loss Bremsstrahlung Tracker momentum matches well with ECAL energy loss, energy scale is correct CRAFT momentum p measured in the CMS silicon tracker dE: energy from ECAL cluster dx: length traversed in ECAL crystals dE/ρdx energy deposit matched to the track corrected for muon path length Experimental data vs Expected stopping power for PbWO 4 from literature Not a fit ! CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09

23. LHC Beam (Sept. 2008) Some Results CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09

24. First LHC Beam in 2008 “Splash” Event Wed, 10 Sept. 2008 “Splash” events observed when beam (450 GeV, 4.10 9 p) struck closed collimators 150m upstream of CMS Halo muons observed once beam (uncaptured and captured) started passing through CMS Data-taking with LHC beam. High energy deposit in the calorimeters, particles travelling horizontally useful to commission forward detectors All systems ON except Tracker and Solenoid CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09

25. Commissioning ECAL with first beam Beam Splash Events: Single beam shots of 2  10 9 protons onto closed collimators 150m upstream of CMS Longitudinal views BEAM Debris Transverse views BEAM Collimators 146m CMS Debris Beam Splash Schematic BEAM 450 GeV A “wave” or “splash” of secondary particles passed through CMS, depositing a huge amount of energy ECAL Energy CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09

26. Beam Splash: ECAL Energy More than 99% of ECAL channels fired Estimated hundreds of thousands of muons passing through CMS per event ~200 TeV energy deposited in EB+EE Inter-crystals timing established (< 1ns), inter-crystal calibration: EB (1.5-2.5% - test beam + cosmics), EE (~7% from splash events) White areas: channels masked from readout ECAL Endcaps crystal index ix crystal index iy crystal index ix crystal index iy Energy (GeV) TOP BOTTOM ECAL Barrel crystal index i  crystal index i  Energy (GeV) CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09

27. Average energy per crystal over 50 splashes: 5-8 GeV Patterns: –shielding structures (square) and floor of the LHC tunnel (bottom) –lower energy at large radius of downstream EE, due to shielding effect of barrel EE pre-calibrations (spread 25%): –Measurements from laboratory applied (precision of 9%): smoother and enhanced patterns –New set being derived assuming local uniformity, to be combined with lab measurements for better startup values CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09 Beam Splash: ECAL Energy

28. CMS TAN TCTV TCTH TCLP BEAM Correlation between Energies in barrel HCAL and ECAL Correlation between ECAL & Beam Loss Monitors ~150 TeV deposited in ECAL & ~1000 TeV deposited in HCAL per splash event Beam Splash Correlations CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09

29. Beam Splash: ECAL Timing Muons RED is a profile of the raw data, and BLUE is the nominal timing according to the equation above. Observed pattern is due to pre-synchronization obtained with laser light Latency then adjusted w/ splashes:hardware allows steps of 1ns steps Further synchronization applied inoffline reconstruction, better than 1 ns Synchronization from splashes will bestart-up condition; better precision w/LHC data Beam splash events provide asource of synchronous hitsthroughout detector, allowingto internally synchronize ECAL CMS ECAL PerformanceFirst LHC Beam – ECAL Perfomance C. Biino – ICATPP 09 Laser distribution modularity

30. Shutdown activities: 1 st maintenance cycle CMS ECAL statusShutdown Activities C. Biino – ICATPP 09 * Only a few/mille channels are not functioning

31. Preshower: –Installed in the months of February-March 2009 –First data collected to check out components and connections  same status of health as in the laboratory, prior to installation: 99.88% good channels (tot 137k) MIP Signal/noise: 3.6 in low gain (physics) and 9 in high gain (calib) Crystal calorimeter: EB and EE active through LHC beams and extended cosmic ray run in 2008/2009  More than 99.5% of the channels are in good health for physics  System routinely operated in CMS global exercises, collecting data to monitor thedetector and consolidate data acquisition and procedures  Trigger commissioning in the endcaps: first data collected, being finalized Beam pipe preshower HCAL EE ECAL status of the detector CMS ECAL statusShutdown Activities C. Biino – ICATPP 09

32. Closing of CMS: 2009 CMS is now closed after a 7-months long and successful maintenance period and is moving again into “beam-ready” state CMS ECAL statusShutdown Activities C. Biino – ICATPP 09

33. Conclusions Crystal part of CMS Electromagnetic calorimeter has collected data with LHC circulating beams and during cosmic ray test runs Preshower detector installed in feb-march 09 –Optimal health –Joined CMS global runs Beam splash events allowed to validate performance and improve: –Endcap startup calibrations –Internal synchronization Long cosmic ray run has allowed to validate energy scale in the barrel and assess stability of temperature and transparency monitoring, both matching specifications CMS ECAL on track for first LHC collision data CMS ECAL statusECAL Detector C. Biino – ICATPP 09

34. Spares

35. CMS ECAL Performance ECAL CalibrationC. Biino – ICATPP 09 precision vs  index (ring) Intercalibration precision at start-up ECAL Barrel: –0.3% on 10 SM (electron beams) –1.5-2.5% on 26 SM (cosmic rays) ECAL Endcaps: –10  15% (LY measurement  VPT gain) High energy electron test beam (0.3%)  “Single crystal maximum response” Cosmic ray calibration (1.5-2.5%)  Muons aligned to crystal axis  Reference signal  250 MeV Crystal LY and transmission (4%)  Co-60 gamma source –Both validated against test beam data 36 Supermodules (100%) intercalibrated with cosmics electron beam calibration reproducibility (Aug - Sept)  /  2 = 0.2% 10 Supermodules (25%) intercalibrated with e - Precalibration 1%

36. Light injected into each crystal using quartz fibres, via the front (Barrel) or rear (Endcap) Laser pulse to pulse variations followed with PN diodes to 0.1% Normalise calorimeter data to the measured changes in transparency Transparency and colour centres: These form in PbWO 4 under irradiation Partial recovery occurs in a few hours Damage and recovery during LHC cycles tracked with a laser monitoring system; 2 wavelengths: 440 nm and 796 nm Black: irradiation at test beam Red: after correction 1% Reference diode Transparency correction: Response to laser pulses relative to initial response provides correction for loss of light yield loss PbWO 4 Test beam irradiation exercises showed precision of correction of 0.15% on several channels ECAL Laser monitoring system CMS ECAL Performance ECAL Calibration & MonitoringC. Biino – ICATPP 09

37. ECAL: laser calibration chain ready Data from a 300 h sequence RMS (APD/PN)(RMS) VPt/PN J.Malcles & laser team % Readout of PN ref working < 1 permill reproducibility achieved LED ‘stabilizer’ pulsing fully commissioned for endcaps Missing FEDs used for development EE+ EE- On EE- concurrent with LED load test CMS ECAL Performance ECAL Calibration & MonitoringC. Biino – ICATPP 09 CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09

38.   RMS (%) Most of EB: stability better 1‰ In absence of transparency variation, the stability of the monitoring system can be assessed Laser data collected throughout CRAFT; laser sequence loops over all ECAL channels every 20 minutes; For each channel and each sequence (600 events), the average is employed as monitoring variable “Stability” is defined as the RMS over all laser sequences of normalized Stabilities are computed for each channel on a period of 200 hours with stable laser conditions APDref is chosen as a reference because of readout problems with PN reference diodes, which are being fixed White regions lack statistics (2 supermodules were not readout for LV problems, now fixed) CMS preliminary Transparency monitoring stability (1) CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09 CRAFT

39. Mean = 0.3 ‰ RMS = 0.2 ‰ 99.6% of channels with RMS<1‰ 99.9% of channels with RMS<2‰ CMS preliminary 1-d projection of map in previous slide Transparency monitoring system stable in EB to better than than 2‰ in 99.9% of the channels (Consistent with specifications needed to achieve the design resolution) Transparency monitoring stability (2) CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09 CRAFT

40. °C Average spread: 0.009 °C CMS preliminary EB equipped with one precision temperature sensor every 10 channels, in good thermal contact with APD and crystal For each sensor, thermal stability is quantified with the RMS of the temperature measurements over one month of data taking The observed stability is 0.009°C on average and better than 0.05°C in all the channels. 1 month Temperature stability during CRAFT CMS ECAL Performance CRAFT – ECAL Perfomance with CosmicsC. Biino – ICATPP 09 CRAFT

41. At the end of CRAFT fully readout ( albeit with some synch problems on few FEDs) Latency scan performed Data being analysed ES residuals: distribution dominated by track extrapolation error Preshower fully part of CMS CMS ECAL statusShutdown Activities C. Biino – ICATPP 09

42. Following a meeting with the LHC people, experiments and CERN management the plan to restart has been agreed. Once collisions at injection energy are established will move to collision at 7 TeV center-of-mass energy. In consultation with experiments and LHC operation will move to higher energy once some luminosity will be accumulated by the experiments and experience gained by the machine operations. Prospects for 2009-2010 Run CMS ECAL statusShutdown Activities C. Biino – ICATPP 09

43. Early Physics Programme Detector commissioning – much already done using cosmics/testbeam,.. Early beam: splash events, first collisions at injection energy, then at 7 TeV Detector synchronization, alignment with beam-halo events, minimum-bias events. Earliest in-situ alignment and calibration Early beam - collisions, up to 10-20 pb -1 @ 7 TeV Commission trigger, start “physics commissioning” – “rediscover SM”: Physics objects; measure jet and lepton rates; observe W, Z, top And, of course, first look at possible extraordinary signatures… 7 TeV, up to 100 pb -1 measure Standard Model, start searches Per pb -1 : 3000 W  l (l = e,  ); 300 Z  ll (l =e,  ); 5 ttbar   +X Improved understanding of physics objects; jet energy scale from W  j j’; extensive use (and understanding) of b-tagging Measure/understand backgrounds to SUSY and Higgs searches Early look for excesses from SUSY & Z’ resonances. Collisions at higher energy: extend searches; Explore large part of SUSY and resonances at ~ few TeV ~ 1000 pb -1 entering Higgs discovery era CMS PhysicsEarly Physics Prospects C. Biino – ICATPP 09