2008 JINST 3 S The CMS experiment at the CERN LHC THE CERN LARGE HADRON COLLIDER: ACCELERATOR AND EXPERIMENTS.

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1 PUBLISHED BY INSTITUTE OF PHYSICS PUBLISHING AND SISSA RECEIVED: January 9, 2008 ACCEPTED: May 18, 2008 PUBLISHED: August 14, 2008 THE CERN LARGE HADRON COLLIDER: ACCELERATOR AND EXPERIMENTS The CMS experiment at the CERN LHC CMS Collaboration ABSTRACT: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and leadlead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to cm 2 s 1 (10 27 cm 2 s 1 ). At the core of the CMS detector sits a high-magneticfield and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values ( η 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of t. KEYWORDS: Instrumentation for particle accelerators and storage rings - high energy; Gaseous detectors; Scintillators, scintillation and light emission processes; Solid state detectors; Calorimeters; Gamma detectors; Large detector systems for particle and astroparticle physics; Particle identification methods; Particle tracking detectors; Spectrometers; Analogue electronic circuits; Control and monitor systems online; Data acquisition circuits; Data acquisition concepts; Detector control systems; Digital electronic circuits; Digital signal processing; Electronic detector readout concepts; Front-end electronics for detector readout; Modular electronics; Online farms and online filtering; Optical detector readout concepts; Trigger concepts and systems; VLSI circuits; Analysis and statistical methods; Computing; Data processing methods; Data reduction methods; Pattern recognition, cluster finding, calibration and fitting methods; Software architectures; Detector alignment and calibration methods; Detector cooling and thermo-stabilization; Detector design and construction technologies and materials; Detector grounding; Manufacturing; Overall mechanics design; Special cables; Voltage distributions IOP Publishing Ltd and SISSA

2 Contents CMS Collaboration ii 1 Introduction General concept 2 2 Superconducting magnet Overview Main features of the magnet components Superconducting solenoid Yoke Electrical scheme Vacuum system Cryogenic plant Other ancillaries Operating test Cool-down Charge and discharge cycles Cold mass misalignment Electrical measurements Yoke mechanical measurements Coil stability characteristics Coil warm-up 25 3 Inner tracking system Introduction Requirements and operating conditions Overview of the tracker layout Expected performance of the CMS tracker Tracker system aspects Pixel detector Pixel system general Sensor description Pixel detector read-out The pixel barrel system The forward pixel detector Power supply Cooling Slow controls Silicon strip tracker Silicon sensors 55 xxiv

3 3.3.2 Read-out system Silicon modules Tracker Inner Barrel and Disks (TIB/TID) Tracker Outer Barrel (TOB) Tracker EndCaps (TEC) Geometry and alignment Detector control and safety system Operating experience and test results 82 4 Electromagnetic calorimeter Lead tungstate crystals The ECAL layout and mechanics Photodetectors Barrel: avalanche photodiodes Endcap: vacuum phototriodes On-detector electronics Off-detector electronics Global architecture The trigger and read-out paths Algorithms performed by the trigger primitive generation Classification performed by the selective read-out Preshower detector Geometry Preshower electronics ECAL detector control system Safety system Temperature Dark current HV and LV Detector calibration Laser monitor system Laser-monitoring system overview Energy resolution Hadron calorimeter Barrel design (HB) Endcap design (HE) Outer calorimeter design (HO) Forward calorimeter design (HF) Read-out electronics and slow control HF luminosity monitor Forward detectors 156 xxv

4 6.1 CASTOR Zero degree calorimeter (ZDC) The muon system Drift tube system General description Technical design Electronics Chamber assembly, dressing, and installation Chamber performance Cathode strip chambers Chamber mechanical design Electronics design Performance Resistive Plate Chamber system Detector layout Readout electronics Low voltage and high voltage systems Temperature control system Gas system Chamber construction and testing Optical alignment system System layout and calibration procedures Geometry reconstruction System commissioning and operating performance Trigger Calorimeter trigger Muon trigger Global Trigger Trigger Control System Data Acquisition Sub-detector read-out interface The Trigger Throttling System and sub-detector fast-control interface Testing The Event Builder The Event Filter Networking and Computing Infrastructure DAQ software, control and monitor Detector Control System Detector infrastructures and safety systems Detector powering 283 xxvi

5 10.2 Detector cooling Front-end electronics cooling Cryogenics Detector cabling Detector moving system Sliding system Pulling system The Detector Safety System DSS Requirements DSS Architecture CMS Implementation of DSS Beam and Radiation Monitoring systems Introduction Protection systems Monitoring systems Computing Overview Application framework Data formats and processing Computing centres Computing services System commissioning and tests Conclusions 307 CMS acronym list 309 Bibliography 317 xxvii