Panic 05, 27 th Oct 2005Q. Ingram, PSI1 The Lead Tungstate Electromagnetic Calorimeter of CMS Q. Ingram on behalf of the CMS Electromagnetic Calorimeter Group Annecy, Demokritos, Belgrade, Bhabha, Bristol, Brunel, Caltech, CERN, Cyprus, Delhi, Dubna, Ecole Polytechnique, ETHZ, Imperial College, Ioannina, Lisbon, Lyons, Milan-Bicocca, Minnesota, Minsk, INR-Moscow, Lebedev Institute, Northeastern, Protvino, PSI, RAL, ENEA- Rome, La Sapienza U, Saclay, Split, Taiwan Central U, Taiwan U, Turin, Yale, Yerevan CMS, Goals, ECAL Lead Tungstate Photo-detectors & Electronics Assembly Calibration & monitoring Test beam results

Panic 05, 27 th Oct 2005Q. Ingram, PSI2 Compact Muon Solenoid (CMS) 21.6 m long x 15 m diameter; 12.5 k tonnes; 4 Tesla solenoid 7 TeV protons Electro- Magnetic Calorimeter (ECAL) Superconducting Solenoid (4T) Muon Chambers Silicon Tracker Hadron Calorimeter Return Yoke 7 TeV protons

Panic 05, 27 th Oct 2005Q. Ingram, PSI3 Recent Photos of CMS Assembly Muon drift chambers mounted in barrel part of the yoke End-cap Muon cathode strip proportional chambers

Panic 05, 27 th Oct 2005Q. Ingram, PSI4 Inserting superconducting coil into vacuum tank Magnet inserted into the outer tank September 2005 Inner vacuum tank inserted October Coil is 12.5 m long 6 m Ø Magnetic Pressure (4 Tesla): 60 bar

Panic 05, 27 th Oct 2005Q. Ingram, PSI5 Standard Model Higgs (9/05) M H < 186 GeV, 95% C.L. Exclusion plot from LEP working group: H → γγ is good discovery channel (also for lightest SUSY Higgs) Discovery of Higgs is major goal of CMS. For M H near minimum allowed by LEP (114 GeV)

Panic 05, 27 th Oct 2005Q. Ingram, PSI6 H  1 year at High Luminosity ( cm -2.s -2 ) Background subtracted Background irreducible – need good energy resolution

Panic 05, 27 th Oct 2005Q. Ingram, PSI7 Resolution Goal  E/E = a /  E  b/E  c Aim: Barrel End cap Stochastic term (a) 2.7% 5.7% (p.e. statistics, shower fluctuations, leakage, …) Noise (b) 155 MeV 770 MeV Low L 210 MeV 915 MeV High L Constant term (c) 0.55% 0.55% (gain stability, non-uniformities, inter-calibration,…)

Panic 05, 27 th Oct 2005Q. Ingram, PSI8 LHC/ECAL Conditions Every 25 nsec: 20 events, 1000 tracks in detector (high luminosity)  fast, high granularity, triggering capability High radiation levels: direct from collisions. In ECAL Barrel ≤ 4 kGy 1 MeV neutron “soup” ≤ n cm -2 (x in End-caps)  high radiation tolerance ECAL detector is barely or practically unserviceable  very high reliability

Panic 05, 27 th Oct 2005Q. Ingram, PSI9 ECAL Endcaps: Crystals (1 type) 30 x 30 x 220 mm 3 (24.7 X 0 ) Vacuum photo-triodes Barrel: 36 Supermodules (18 per half-barrel) Crystals (34 types) ~ 24 x 24 x 230 mm 3 (25.8 X 0 ) Avalanche photo-diodes All channels’ gains monitored with laser Crystals point 3º off vertex Pb/Silicon pre-shower for π°/γ discrimination (3 X 0 ) 7.9 m 3.6 m Compact, homogeneous, within magnet, precise 90 tonnes 4 Modules per Supermodule Fast, high granularity Radiation “hard”

Panic 05, 27 th Oct 2005Q. Ingram, PSI10 Lead Tungstate (PbWO 4 ) Compact calorimeter: CMS more compact, cheaper Homogeneous calorimeter: excellent energy resolution High density8.28 g/cm 3 Short radiation length0.89 cm Small Moliere radius2.19 cm Short decay time10 nsec Cost (was) 1.6 $ /cm 3 Peak light emission430 nm Temperature Coeff- 2%/ ºC Refractive Indexca 2.2 Light yield~ 5% of BGO Radiation “hard”: scintillation and emission not affected, but transmission reduced by formation of colour centres  constant monitoring

Panic 05, 27 th Oct 2005Q. Ingram, PSI11 PbWO 4 Quality Control Automatic testing of dimensions, transmission, light yield, longitudinal uniformity Sharpness of transmission edge indicator of radiation resistance (Crystals from Bogoroditsk, Russia) Crystals from Shanghai all tested after irradiation

Panic 05, 27 th Oct 2005Q. Ingram, PSI12 Photo-Detectors (APDs, VPTs) Requirements: - Gain (low light yield of PbWO 4 ) - Operation in 4 Tesla field - Radiation hard (10 yrs: n/cm 2 in Barrel, > n/cm 2 in End-caps) - High reliability (99.9%) over 10 years - unserviceable Solutions: -Avalanche Photo-diodes (APDs) in Barrel: gain 50 -Vacuum Photo-triodes (VPTs) in End-caps (axial field): gain Both specially developed for CMS APDs: Hamamatsu VPTs: RIE St Petersburg

Panic 05, 27 th Oct 2005Q. Ingram, PSI13 APD Structure Photo-electrons from THIN 6 μm p-layer induce avalanche at p-n junction Electrons from ionising particles traversing the bulk NOT amplified (insensitive to shower leakage) 2 APDs (each 5 x 5 mm) mounted in capsule for gluing to crystal

Panic 05, 27 th Oct 2005Q. Ingram, PSI14 Some APD Properties (Gain=50) Active area 5 x 5 mm Charge collection within 20 nsec99 ± 1% Capacitance 80 pF (fully depleted) Dark Current (Id) before irradiation< 50 nA (~ 5 nA typical) Voltage sensitivity (1/M*dM/dV)3.15 % / V Temperature sensitivity (1/T*dM/dT)- 2.4 % /  C Excess noise factor2.1 Radiation Hardness: After 10 years LHC equivalent hadron irradiation, ONLY change is the dark current,  5 μA Aging: No effect seen after ca 10 years’ equivalent in an oven. Acceptance tests: to ensure 99.9% reliability, all APDs screened by 5 kGy 60 Co irradiation + 4 weeks cooking at 80  C and tested to gain 300 (few % rejected)

Panic 05, 27 th Oct 2005Q. Ingram, PSI15 Vacuum Photo-Triodes (VPTS) B-field orientation favourable Gain at B = 4 T Radiation hard (UV glass window) Active area of ~ 280 mm 2 /crystal Q.E. ~ 20% at 420 nm  = 26.5 mm MESH ANODE Single stage photomultiplier tube with fine metal grid anode All tested at 1.8 T (10% at 4T)

Panic 05, 27 th Oct 2005Q. Ingram, PSI16 On-detector Electronics 800 Mb/s optical links to upper-level Custom designed ASICS in IBM 0.25  m technology multi-gain shaping amplifier. Gain 1, 6 & 12 for dynamic range of ns sampling 12-bit ADC with base-line detection. Selects gain Build, send trigger primitives; store data (3  s latency) Fast Xtal and photo- detector Crystal APD/VPT ADC Upper Level Readout few ns 50 ns Digital Trigger Sum 25 channels To ULR To Trigger   Pipeline

Panic 05, 27 th Oct 2005Q. Ingram, PSI17 Electronics Performance Noise 2003 data - 44 MeV noise in single channel (40 MeV in 2004 data) - Negligible correlated noise 9 Crystals 25 Crystals Resolution 120 GeV electrons Sum over 3 x 3 matrix. Only electrons entering centre of central crystal – minimises containment and cross-calibration errors Excellent intrinsic resolution 2004 data

Panic 05, 27 th Oct 2005Q. Ingram, PSI18 ECAL Barrel Assembly 2 APDs in capsule Capsule mounted on Xtal 10 Xtals in submodule alveolar (0.1 mm walls glass-fibre/epoxy with Al lining) 10 kg 4 modules in each of 36 “Supermodules” (1700 Xtals, 2 tons) submodules in a module 0.5 ton

Panic 05, 27 th Oct 2005Q. Ingram, PSI19 Adding the Electronics TestingTidying

Panic 05, 27 th Oct 2005Q. Ingram, PSI20 ECAL End-Caps and Pre-Shower 25 Xtals in a “Supercrystal” ca 40 kg 3662 Xtals in a half-Dee 6 tons Pre-shower Detector 1.4 x10 5 ch of 1.9 mm Si strips behind Pb layers - 10 o C for rad hardness 2 half-Dees per End-cap

Panic 05, 27 th Oct 2005Q. Ingram, PSI21 Calibration Pre-(inter)calibration rms Initial channel-to-channel variation: 8% Apply crystal light yield lab data & APD gain 4% Calibrate in high energy electron beam < 2% no beam till 6/06 Calibrate with cosmic rays 2-3% in 1 week In situ calibration Intercalibrate over Φ using jet energy deposit with high (>120 GeV) E T triggers2-3% in 2 hours Calibrate over Φ and cross-calibrate over η with Z → e + e - 1% in 1 day Final calibration with W → e (E/p comparison – needs Tracker) 0.5% in few months

Panic 05, 27 th Oct 2005Q. Ingram, PSI22 Pre-Intercalibration a) Get intercalibration coeffs. from lab light-yield and APD gain data. Compare to beam result: From beam From lab Agree to 4% b) With cosmic rays - Cosmic muons deposit 250 MeV OK over full length - use adjacent crystals as veto counters - Electronics noise 40 MeV rms: raise APD gain from 50 to % statistical precision in 1 week on full 1700 Supermodule channels. ca 3% agreement (preliminary, short run) with beam results Also vitally important full system debugger

Panic 05, 27 th Oct 2005Q. Ingram, PSI23 Laser Monitoring Radiation damage  reduced crystal light transmission Self-annealing  (partially) restored light transmission Net effect: light reduction saturates depending on dose rate light output varies with LHC beam conditions  Monitor transmission with laser Light injected through fibres into each crystal Laser stability monitored by PN diode (< 0.1%)

Panic 05, 27 th Oct 2005Q. Ingram, PSI24 Laser Monitoring Electron/laser pulse comparison High beam rate (damage) Low beam rate (recovery) Electron (S) / laser (R) correlation: S/S 0 = (R/R 0 ) 1.6 Power ≠ 1 because laser path shorter

Panic 05, 27 th Oct 2005Q. Ingram, PSI25 Performance in 2004 Test Beam Resolution 120 GeV electrons Sum over 3 x 3 matrix. Uniform illumination of crystal front Xtal 704 Energy (GeV)  E/E = 3.0 /  E  166 (MeV) /E  Crystals

Panic 05, 27 th Oct 2005Q. Ingram, PSI26 Schedule Schedule is very tight, driven by crystal production But we expect that Barrel will be installed for pilot run in late 2007 End-caps will be installed for first physics run in 2008 Dates are subject to the LHC schedule which is also very tight

Panic 05, 27 th Oct 2005Q. Ingram, PSI27 Summary CMS Electromagnetic Calorimeter is compact, precise, fast, highly granular, radiation tolerant Major components specially developed for ECAL new technologies (PbWO 4, APDs) - now being used in other detectors Test with beam and monitoring system show that performance should meet design goals H   discovery possible in 2-3 years at low luminosity Installation in CMS “just-in-time”