Development of a tracking detector for physics at

Development of a tracking detector for physics at the Large Hadron Collider Geoff Hall G Hall October 2002

CMS = Compact Muon Solenoid detector • missing element in current theoretical framework - mass Total weight Diameter Length Magnetic field 12, 500 tons 15 m 21. 6 m 4 T Tracking system 10 million microstrips Diameter 2. 6 m Length 7 m Power ~50 k. W G Hall 2 October 2002

LHC parameters (CMS) • Consequences High speed signal processing Signal pile-up High (low) radiation exposure High (low) B field operation Very large data volumes New technologies G Hall 3 October 2002

Design philosophy • Large solenoidal (4 T) magnet iron yoke - returns B field, absorbs particles technically challenging but smaller detector, p resolution, trigger, cost • Muon detection high p. T lepton signatures for new physics • Electromagnetic calorimeter high (DE) resolution, for H => gg (low mass mode) • Tracking system momentum measurements of charged particles pattern recognition & efficiency complex, multi-particle events complement muon & ECAL measurements improved p measurement (high p) E/p for e/g identification G Hall 4 October 2002

Parameters for hadronic collider physics • E, p, cosq, f prefer variables which easily Lorentz transform e. g E, p. T, p. L, f • p. T divergences from simple behaviour could imply new physics eg heavy particle decay => high p. T lepton (or hadron) • rapidity Lorentz boost => invariant • pseudorapidity LHC G Hall H~ 6 |h| < 2. 5 5 October 2002

Physics requirements (I) • Mass peak - one means of discovery => small s(p. T) eg H => ZZ or ZZ* => 4 l± typical p. T(µ) ~ 5 -50 Ge. V/c • Background suppression measure lepton charges good geometrical acceptance - 4 leptons background channel t => b => l require m(l+l-) = m. Z GZ ~ 2. 5 Ge. V precise vertex measurement identify b decays, or reduce fraction in data G Hall 6 October 2002

Physics requirements (II) • p resolution large B and L • high precision space points detector with small intrinsic smeas • well separated particles good time resolution low occupancy => many channels good pattern recognition • minimise multiple scattering • minimal bremsstrahlung, photon conversions material in tracker most precise points close to beam G Hall 7 October 2002

Silicon diodes as position detectors • Spatial measurement precision defined by strip dimensions ultimately limited by charge diffusion s ~ 5 -10µm G Hall 8 October 2002

Vertex detector ~1990 G Hall 9 October 2002

Interactions in CMS 7 Te. V p G Hall 10 October 2002

Microstrip tracker system 2. 4 m ~10 M detector channels ~ 6 m G Hall 11 October 2002

Event in the tracker G Hall 12 October 2002

Silicon detector modules • Constraints on tracker minimal material high spatial precision sensitive detectors requiring low noise readout power dissipation ~50 k. W in 4 T magnetic field radiation hard Budget • Requirements large number of channels limited energy resolution limited dynamic range G Hall 13 October 2002

Radiation environment • Particle fluxes Charged and neutral particles from interactions ~ 1/r 2 Neutrons from calorimeter nuclear backsplash + thermalisation ≈ more uniform gas only E > 100 ke. V damaging • Dose energy deposit per unit volume Gray = 1 Joule/kg = 100 rad mostly due to charged particles G Hall 14 October 2002

Imperial College contributions to Tracker APV 25 APVMUX/PLL FED G Hall 15 • • Hardware development Hardware construction Beam tests & studies Preparation for physics October 2002

APV 25 0. 25µm CMOS 1 of the 128 channels Analogue unity gain inverter SF Low noise charge preamplifier SF 50 ns CRRC shaper programmable gain 192 -cell analogue pipeline S/H 128: 1 Differential current MUX O/P signal processing & pipeline amplifiers memory MUX APSP control logic APV 25 -S 1 (Aug 2000) Chip Size 7. 1 x 8. 1 mm Final APV 25 -S 0 G Hall (Oct 1999) 16 October 2002

Chip testing • Automated on-wafer testing ~1 min/site ~100, 000 to test G Hall 17 October 2002

Irradiations of 0. 25µm technology • Extensive studies CMS tracker data from IC, Padova, CERN ALL POSITIVE and well beyond LHC range PMOS • CMOS hard against bulk damage Qualify chips from wafers with ionising sources • Typical irradiation conditions 50 k. V X-ray source Dose rate ~ 0. 5 Mrad/Hour to 10, 20, 30 & 50 Mrad G Hall PMOS 2000/0. 36 400µA 18 October 2002

APV 25 irradiations (IC & Padova) • IC x-ray source Normal operational bias during irradiation clocked & triggered Post irradiation noise change insignificant pre-rad APV 25 -S 1 also 10 Me. V linac electrons(80 Mrad) G Hall and 19 10 Mrad 2. 1 x 1014 reactor n. cm-2 October 2002

Silicon as a detector material • Detectors operated as reverse biased diode dark current = noise source signals small typical H. E. particle ~ 25000 e 300µm Si 10 ke. V x-ray photon ~ 2800 e • Deplete entire wafer thickness Vbias ~ NDd 2 ND ~ 1012 cm-3 => Vbias ~ 50 V for 300µm ND : NSi ~ 1 : 1013 ultra high purity • Further refining required Float Zone: local crystal melting with RF heating coil G Hall 20 October 2002

Radiation effects in (bulk) silicon • Silicon atoms dislodged from lattice sites… causing more damage as they come to rest. . . after irradiation increased dark currents altered substrate doping primary defects = V & I diffuse and become trapped influenced by O & C impurity levels G Hall 21 October 2002

CMS Silicon Strip Tracker Front End Driver 96 Tracker Opto Fibres CERN Opto. Rx Analogue/Digital 9 U VME 64 x Data Rates 12 JTAG 9 U VME 64 x Form Factor Modularity matched Opto Links 12 FE-FPGA Cluster Finder 12 FPGA Configuration VME Interface VME-FPGA BE-FPGA Event Builder 12 TCS Analogue: 96 ADC channels (10 -bit @ 40 MHz ) @ L 1 Trigger : processes 25 K MUXed silicon strips / FED TTCrx 12 Buffers DAQ Interface 12 Raw Input: 3 Gbytes/sec* after Zero Suppression. . . DAQ Output: ~ 200 MBytes/sec 12 Temp Monitor 12 Front-End Modules x 8 Double-sided board G Hall Xilinx Virtex-II FPGA Power DC-DC ~440 FEDs required for entire SST Readout System TCS : Trigger Control System 22 *(@ L 1 max rate = 100 k. Hz) October 2002

averages Delay Line G Hall a d a 16 8 averages 8 16 8 d DPM 8 s-data 8 s-addr hit No hits Sequencer-mux status 11 a d a 16 8 Synch in Synch out emulator in Synch error Global reset Sub resets Full flags control 4 data 160 MHz Serial I/O Local IO 11 trig 3 nx 256 x 16 DLL 8 256 cycles Hit finding trig 2 Re-order cm sub 10 Ped sub 10 header Temp Sensor Opto Rx trig 1 sync ADC 12 Phase Registers 256 cycles 10 Synch d Clock 40 MHz Control 8 16 mux status 8 s-data 8 s-addr hit No hits DPM 11 trig 4 4 x header trig 3 nx 256 x 16 Sequencer-mux 11 256 cycles Hit finding 10 trig 2 Re-order cm sub 10 Ped sub trig 1 sync 10 Phase Registers 2 x 256 cycles ADC 1 1 x 2 x 4 x Cluster Finding FPGA VERILOG Firmware Packetiser per adc channel phase compensation required to bring data into step Front-End FPGA Logic Serial Int CMS Silicon Strip Tracker FED + Raw Data mode, Scope mode, Test modes. . . 23 B’Scan Config October 2002

The CMS Tracking Strategy • Rely on “few” measurement layers, each able to provide robust (clean) and precise coordinate determination 2 -3 Silicon Pixel 10 - 14 Silicon Strip Layers Number of hits by tracks: Total number of hits Double-side hits in thin detectors Double-side hits in thick detectors Radius ~ 110 cm, Length/2 ~ 270 cm 6 layers TOB 4 layers TIB 3 disks TID G Hall 9 disks TEC 24 October 2002

Vertex Reconstruction Primary vertices: use pixels! At high luminosity, the trigger primary vertex is found in >95% of the events G Hall 25 October 2002

High Level Trigger & Tracker DAQ of the events should survive. 40 MHZ “How can I kill these events using the least CPU time? ” This can be interpreted as: o The fastest (most approx. ) reconstruction o The minimal amount of precise reconstruction o A mixture of the two 100 KHz 100 Hz HLT Track finding Events rejected at HLT are irrecoverably lost! G Hall In High Level trigger reconstruction only 0. 1% Same SW would be use in HLT and off-line : algorithms should be high quality algorithms should be fast enough 26 October 2002

References • A. Litke & A. Schwarz Scientific American May 1995 • T. Liss & P. Tipton Scientific American September 1997 • N. Ellis & T. Virdee. Experimental Challenges in High Luminosity Collider Physics. Ann. Rev. Nucl. Part. Sci 44 (1994) 609 -653. • G. Hall Modern charged particle detectors Contemporary Physics 33 (1992) 1 -14 & refs therein • G. Hall Semiconductor particle tracking detectors Reports on Progress in Physics. 57 (1994) 481 -531 • A. Schwarz 1993 Heavy Flavour Physics at Colliders with silicon strip vertex detectors. Physics Reports 238 (1994) 1 -133. • C. Damerell Vertex detectors: The state of the art and future prospects. Rutherford Appleton Laboratory report RAL-P-95 -008 A pdf version is available on the CERN library Web site. (Search preprints) • CMS Web pages http: //cmsdoc. cern. ch/cmsnice. html • http: //cmsinfo. cern. ch/Welcome. html Letter of Intent (most readable) and Technical proposal • http: //cmsdoc. cern. ch/cms/TDR/TRACKER/tracker. html CMS Tracker Technical Design Report (even more detail on many aspects) of the tracker. G Hall 27 October 2002