PPRP September 2002 UK CMS 1 CMS Endcap Electromagnetic Calorimeter and Global Calorimeter Trigger, Physics & Computing Presented by Peter Hobson, Brunel University on behalf of Bristol University Brunel University Imperial College of Science, Technology & Medicine RAL

PPRP September 2002 UK CMS 2 The Compact Muon Solenoid Detector for LHC Physics goals: SUSY, Higgs, Heavy flavours, heavy ions Endcap Electromagnetic Calorimeters

PPRP September 2002 UK CMS 3 ECAL design objectives High resolution electromagnetic calorimetry is a basic design objective of CMS Benchmark physics process: Sensitivity to a low mass Higgs via H

PPRP September 2002 UK CMS 4 ECAL Parameters 3° off-pointing pseudo- projective geometry 3.5 m 6.3 m

PPRP September 2002 UK CMS 5 UK Commitments Develop and prototype photodetectors Procure and test photodetectors Design and prototype Supercrystals Design and procure Supercrystal mechanics and HV Design and procure Supercrystal support structures Evaluate lead tungstate crystals for endcap Set up a Regional Centre for Supercrystal production Construct and test Supercrystals and ship to CERN Design, prototype and construct the Global Calorimeter Trigger

PPRP September 2002 UK CMS 6 Photodetectors: end caps Vacuum Phototriodes (VPT) Developed by CMS-UK in conjunction with industry (Western & Russian) Vacuum devices offer greater radiation hardness than Si diodes Gain at B = 4 T Active area of ~ 280 mm 2 /crystal Q.E. ~ 20% at 420 nm UV glass window - less expensive than quartz - more radiation resistant than borosilicate glass = 26.5 mm MESH ANODE Order placed with RIE (Russia): 2600 devices delivered so far and >1600 tested

PPRP September 2002 UK CMS 7 VPT Characterisation 4.0T Superconducting solenoid at Brunel 1.8T Dipole Magnet at RAL A sample of VPTs are measured at B =4.0T and = 15 o at Brunel All VPTs are measured at 0 B 1.8T and -30 o 30 o at RAL

PPRP September 2002 UK CMS 8 VPT Characteristics Response vs. Angle Critical magnetic field and radiation tolerance tests are done in the UK Only 8% loss of transparency after 20 kGy (10 years) 4T test

PPRP September 2002 UK CMS 9 VPT Characteristics Anode response of production VPTs at 1.8T (averaged over 8 O – 25 O ), in units of e - /MeV (using data from beam tests with PbWO 4 ), plotted versus the product of photocathode efficiency and gain, as measured by the manufacturer at 0T On schedule

PPRP September 2002 UK CMS 10 Construction: end caps The endcap is mechanically complex Tight tolerance on dimensions, deflections and thermal management.

PPRP September 2002 UK CMS 11 Construction: end caps Supercrystal: carbon-fibre alveola containing 5x5 tapered crystals + VPTs + HV filter 156 Supercrystals per Dee All crystals have identical dimensions All Supercrystals are identical (apart from inner and outer circumference)

PPRP September 2002 UK CMS 12 Construction: end caps Figure 6. The arrangement of components within a Supercrystal The principal components of a supercrystal: PbWO 4 crystal, VPT, alveolar, optical fibre monitor, HT filter, mechanics

PPRP September 2002 UK CMS 13 Construction: end caps Engineering Design Reviews Supercrystal mechanics approved (332 Carbon-fibre/epoxy alveolar modules (60% of total) have now been produced in Russia to UK design) 2002 – D and backplate mechanics approved Three full-sized supercrystal prototypes completed. These are major milestones achieved. The overall mechanical design is now frozen and the tendering process has begun.

PPRP September 2002 UK CMS 14 Evaluation of endcap crystals Ongoing developments have progressively increased the boule diameter: Two barrel crystals are now cut from a single boule in current production Even larger boules have been grown which could provide four crystals per boule Transmission loss due to irradiation at 15 Gy/h for 24 hours. Induced absorption fitted with Gaussians at 2.3 eV (540nm) and 3.1 eV (400nm). Crystal lab at ICSTM has studied in detail the formation and annealing of colour centres

PPRP September 2002 UK CMS 15 Evaluation of endcap crystals ICSTM crystal laboratory Measurements demonstrate that the low level of light collection non- uniformity means that no special surface/wrapping treatment is needed. This is a crucial result since wrapping increases complexity and cost Correlation between light collection non-uniformity (RNUF) and optical parameters measured at the ICSTM Crystal Laboratory.

PPRP September 2002 UK CMS 16 Original TDR ECAL design cannot be afforded A new scheme (post GPD Mid-term Review) endorsed by CMS in March 2002 Trigger primitive generation now moved to the front-end electronics –Fully digitised data can be restricted to events passing Level 1 trigger –Order of magnitude reduction in number of links and off-detector electronics Major use of Tracker components (optical links, clock and control) and APV25 expertise in 0.25µm technology ECAL Readout architecture

PPRP September 2002 UK CMS 17 CMS Requested the new VFE ASIC (FENIX) be designed by the Microelectronics group at RAL. CMS and PPARC have agreed that the staff costs will be covered from the UK contribution to the 'Cost-to-Completion'. ECAL Readout architecture

PPRP September 2002 UK CMS 18 Global Calorimeter Trigger Global Calorimeter Trigger (GCT) sorts trigger objects and forms energy sums

PPRP September 2002 UK CMS 19 Global Calorimeter Trigger FPGA processing using common module design Data exchange via Gbit serial links UK group developed the use of FPGA technology to implement the algorithms Algorithm development has improved physics coverage and jet trigger performance Milestone: Level-1 Trigger TDR Dec 2000 System design complete, hardware prototyping starting now

PPRP September 2002 UK CMS 20 Physics simulation UK is significantly involved in the Physics Reconstruction and Selection project to maximise our ability to exploit our detectors. ECAL – e/gamma Group Led by a UK Physicist Responsible for all aspects of the ECAL software Tracker – b/tau Group UK physicist leading the data-handling group responsible for all aspects of offline software related to tracker readout/electronics Provides test-beam analysis tools and contributes to the data analysis

PPRP September 2002 UK CMS 21 Physics simulation The data rate is everywhere small compared with the 200 MB/s limit that the DAQ can cope with. Heavy-ion High and low luminosity pp Data rate in the silicon tracker (barrel)

PPRP September 2002 UK CMS 22 Tier 1 centre at RAL for CMS –Fraction of a joint central LHC facility Tier 2 centres in London and S.England –The focus for CMS-UK analysis in the future Major contribution to the production challenge –5 TB data produced in the UK, 6 UK physicists involved Use of GRID computing technology –CMS first in HEP to deploy Grid-based production tools Increasing profile within the CMS Core Computing and Software project CMS computing in the UK

PPRP September 2002 UK CMS 23 Vacuum Phototriodes –Contract placed, delivery on schedule Endcap mechanics –Two major design reviews successfully passed –Tender in process for supercrystal mechanics Crystals –Prototype Endcap crystals evaluated –Pre-production order about to be placed Global Calorimeter Trigger –December 2000 Level 1 trigger Technical Design Report –Prototypes of components will be produced early 2003 Computing –Major contribution to the CMS production exercises –Leading roles in developing ECAL and Tracker related software ECAL, GCT & Computing Summary

PPRP September 2002 UK CMS 24 Crystal delivery –There have been delays in placing the order for endcap crystals. The delivery of crystals is on the critical path. Electronics –Redesign of ECAL electronics has provided large cost savings. However the new and complex system must be successfully prototyped before the production phase. ECAL Concerns

PPRP September 2002 UK CMS 25 Although CMS has encountered problems, this is to be expected in a project of such size and complexity. The problems are being tackled and CMS has Financial Plan and Master Schedule that aims to deliver a full detector in time for physics. UK designing new ASIC for ECAL electronics The cuts made for SCP4 have increased the risks associated with the project substantially. The Travel Budget in future years is of particular concern, as the focus of activities moves to CERN. Overall Summary Despite these concerns, the UK projects are making excellent progress.