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Requirements and status of the CMS ECAL calorimeter

Requirements and status of the CMS ECAL calorimeter. Physics Goals, Energy resolution & LHC environment CMS ECAL design and status Barrel Endcaps Laser monitoring Photodetectors & electronics CMS ECAL schedule Summary. Physics Goals.

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Requirements and status of the CMS ECAL calorimeter

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  1. Requirements and statusof the CMS ECAL calorimeter • Physics Goals, Energy resolution & LHC environment • CMS ECAL design and status • Barrel • Endcaps • Laser monitoring • Photodetectors & electronics • CMS ECAL schedule • Summary

  2. Physics Goals Main goal: precise energy measurements of e, g, p0 Benchmark process : Discovery of Higgs boson through its decay Hgg (A key question for HEP future) Discovery potential driven by photon energy resolution Need for extremely high-precision electromagnetic calorimetry!! 3 first years of LHC !

  3. Energy resolution • a, stochastic term : photostatistics = light yield (+ photosensor) specification <3% achieved for LY > 8 p.e./MeV • b constant term : Non uniformity,Calibration, .... This term dominates above 50 GeV specification: b = 0.005 A small FNUF and the ability to monitor the light losses at 0.3% during the whole operation are essential requirements • c noise term : electronics noise, dark current, pile-up c~ 130 MeV achieved with CMS electronics

  4. LHC conditions • Fast interaction rate (Bunch crossing every 25 ns) • Requires fast crystals (now slow component nor afterglow) • Strong radiation level: at nominal LHC luminosity 10 34 cm-2 s-1 • Dose rate in Barrel ~ .15 to 0.30 Gy/h • Dose rate in endcaps ~ .30 to 15.0 Gy/h ECAL must maintain its performance during 10 years of operation and even be able to continue functioning for possible LHC upgrade (x 5-10 luminosity increase)

  5. CMS ECAL End caps 25X0 1.48< |h| <3.0 14648 crystals Barrel 25.8 X0 |h| <1.48 61200 crystals

  6. ECAL Barrel Sub module 10 crystals Module 400/500 crystals Crystal: 2.2 x 2.2 x 23 cm3(tapered) 2x17 types 1700 crystals per SM 36 SMs (+1 spare) Super Module 4 Modules 1700 crystals

  7. ECAL Barrel Sub Module SuperModule Module Already 14 (out of 37) SuperModules assembled

  8. ECAL Endcaps • Crystal : 3 x 3 x 22 cm3(tapered) . All crystals identical • Super Crystal: 5x 5 channels Supercrystal Mechanics procurement well advanced Base plate

  9. Laser monitoring system To follow damage and recovery of light transmission during LHC cycles, we use a laser system at 440 nm • Inject light in each crystal. • Laser fluctuations measured by PN diodes (0.1 % stability). Other laser at 800 nm to check electronics stability (small radiation damage for this wavelength) • The monitoring system can only follow changes in light transmission: modifications of the scintillation mechanism would be fatal !

  10. Photo-sensors Different for Barrel and Endcaps (different radiation levels, different magnetic field orientation) Barrel APDs , gain 50, 2x 25 mm2 1”End Cap Vacuum Phototriodes All (130K) delivered 8000 (= 55%) delivered

  11. Electronics • New architecture in 2002, to reduce cost and simplify implementation using new Deep-Sub-Micron radiation hard technology • Very successful change: target performance reached in test beam Fall 2003 • First complete SuperModule in test beam October 2004 • Production launched . Capacity to equip 3 SuperModules/months

  12. Trigger GOH FE board QPLL 5 VFE Boards (MGPA +AD1240 + Buffer) CCU Readout GOH FENIXes LVR board Electronics 25 channels ECAL Trigger Tower

  13. CMS & ECAL Schedule • CMS is a complex experiment, which requires a well defined sequence of assembly ECAL Barrel must be inserted early (Nov 2006) to allow the insertion and cabling of the central tracking detector and the beam pipe closure. ECAL Endcaps can be inserted last. • The completion of the full CMS ECAL (Barrel + Endcap) is essential for the physics programme of LHC. Unlike for e+e- experiments, the Endcaps have a strong impact on acceptance due to the angular distribution of produced particles (40% of Higgs events have a photon in one Endcap) • It is therefore mandatory to have EndCaps and Barrel ready for the Physics run scheduled early 2008

  14. ECAL Schedule Taking into account the CMS insertion scenario V34 • The last Barrel SM must be inserted in November 2006 It takes us about 3.5 months between the last delivered crystal and the SuperModule readiness: we need the last Barrel crystal delivered by early July 2006 • The 2nd Endcap must be inserted latest February 2008 we need the last Endcap crystal delivered by early July 2007 • There is no contingency in the above planning: any gain (even one or two months ) compared to these dates would be welcome • The construction schedule is driven by the crystal delivery

  15. Summary • The CMS crystal ECAL is a very challenging project, aiming at 0.5% resolution, over a large volume in a difficult environment. The Quality of the crystals and the ability to monitor damages due to radiation are therefore essential. • All aspects of the project are proceeding well : the mechanical parts are delivered, the monitoring system is complete, the electronics is performing with target performance and is under production. • The schedule is tight, and driven by the crystal delivery. We still need about 36K Barrel crystals (~22K not yet contracted) and 15K Endcaps (not contracted).

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