Detector for a Linear Collider 8th Topical Seminar on Innovative Particle and Radiation Detectors Siena, 21 24 October 2002 Joachim Mnich RWTH Aachen e + e - Linear Collider Projects Physics at a 1 TeV e + e - Linear Collider Implications for Detector Design Vertex Detector Tracking Detector Calorimeter Detector for a Linear Collider Outline: Concepts for an e + e - Linear Collider ( s = 500 GeV 1 TeV) Cavities: superconductive normal Frequency: 1.3 GHz X- (11.4 GHz) or C-Band (5.7 GHz ) Route to higher energies ( s = 5 TeV): CLIC: Acceleration by Drive-Beam A) cms-energy: TESLA-Project (DESY): Technical Design Report March MV/m s = 800 GeV already achieved with improved manufacturing (electropolishing) Superconductive cavities Acceleration gradient 23 MV/m s = 500 GeV 800 GeV Very recent result from 4 nine cell modules: B) Luminosity Strong focussing at the interaction point Simulation Generation of small bunches: Final-Focus-Test (SLAC/DESY) Collision of bunches: Fast feedback system (Bunch separation: 337 ns) use beam deflection/widening after collision kicker magnets, Piezo-crystals TESLA Electron-Positron-Collider Project: Electron-Positron-Annihilation: Cross sections of SM- and MSSM-processes up to 1 TeV e + e ff pb e + e HZ 10 fb (m H 3 (independent of s) Goal: reconstruction of primary vertex (IP) < 5 m 10 m / (p sin 3/2 ) SLD: 8 m 33 m / (p sin 3/2 ) 1. Material budget: Thin detectors 60 m (= 0.06% X 0 ) Minimise support stretched silicon 3 m sagitta for 1.5 N tension Three main issues: Baseline design with 5 layers: Stand alone tracking Internal calibration 3. Readout speed: Integration of background during long bunch train small pixel size (20 m 20 m) to keep occupancy low read 10 times per train 50 MHz clock CCD design 2. Radiation hardness: High background from beam-strahlung and beam halo Much less critical than LHC But much more important than at LEP TESLA (r i = 1.5 cm) CMS (r i = 4.3 cm) Dose ( ,e ,h ) 10 kGy1000 kGy Neutron flux10 10 /cm /cm 2 Vertex detector: Three technologies under consideration 1. Charge Coupled Device Create signal in 20 m active layer etching of bulk to keep total thickness 60 m 800 million pixels (SLD 300 million pixel) Coordinate precision 2-5 m Low power consumption (10 W) But very slow! use column parallel readout CCD classic CP CCD 2. DEPFET (DEPleted Field Effect Transistor) Fully depleted sensor with integrated pre-amplifier Low power: 1 W/sensor Low noise: 10 e at room temperature! Thinning to 50 m possible Result from a 64 64 pixel matrix: 50 m 50 m pixel 9 m reolution To be shown: Column wise readout with 50 MHz 1987 (Kemmer,Lutz) 3. MAPS (CMOS Monolithic Active Pixel Detectors) Standard CMOS wafer, integrates all functions 1999 Same unique wafer for sensor and electronics i.e. no connections like bump bonds Very small pixel size achievable Radiation hardness proven Power consumption pulse power? II. Tracker Study of Higgs production independent of Higgs decay lepton momenta ideally: recoil mass resolution limited by Z width SUSY mass measurements - Pair production of scalar leptons (decay to lepton + neutralino) - Mass determination from end points of Momentum spectra Precise measurement of charged particle momenta: Momentum resolution (1/p t ) < 5 (GeV/c ) -1 (full tracker) Large Si-Tracker la LHC experiments? much lower particle rates at linear collider keep material budget low Large TPC 1.7 m radius 3% X 0 barrel (30% X 0 endcap) high magnetic field (4 Tesla) Goals: 200 points (3-dim.) per track 100 m single point resolution dE/dx 5% resolution 10 times better performance than at LEP New concept for gas amplification at the end flanges: Replace proportional wires with Micro Pattern Gas Detectors - Finer dimensions - Two- dimensional symmetry (no EB effects) - Only fast electron signal - Intrinsic ion feedback suppression GEM or Micromegas Wires GEM Gas Electron Multiplier (GEM) (F. Sauli 1996) 140 m 75 m 50 m capton foil, double sided copper coated 75 m holes, 140 m pitch GEM voltages up to 500 V yield 10 4 gas amplification Use GEM towers for safe operation, e.g. COMPASS Micromegas (Y. Giomataris 1996) asymmetric parallel plate chamber with micromesh saturation of Townsend coefficient mild dependence of amplification on gap variations ion feedback suppression 50 m pitch Disadvantage of electron signal: No signal broadening by induction Signal collected on one pad No centre-of-gravity Possible Solutions: Smaller pads Replace pads by bump bonds of pixel readout chips Capacitive or resistive coupling of adjacent pads Alternative pad geometries Strip couplingchevrons III. Calorimeter Hermiticity to exploit missing energy signature of SUSY No cracks Calorimeter inside magnet coils Fast readout & good time resolution to avoid event pile up Excellent energy and angular resolution - Mass reconstruction e.g. e + e t t - Distinguish hadronic W- and Z-decays e + e t t at threshold Goal for jet energy resolution Jet energy resolution: W/Z identification by mass reconstruction in 4 jets: Include Fig from TDR To get best jet energy resolution: measure every particle in the jet Energy distribution in typical multijet event: 60% charged particles Tracker 30% photons Ecal 10% neutral hadrons Ecal + Hcal + good lepton ID Fine granularity (in 3 dim.) of electromagnetic and hadron calorimeters Combine tracks and clusters From energy flow to particle reconstruction! Highly granular calorimeter: Electromagnetic: identify particles down to low energies longitudinal segmentation X 0 X 0 / small transversal segmentation r M no cracks, magnet coil outside Hadron calorimeter: cell size close to X 0 good cluster separation good energy resolution Si/W natural choice r M = 9 mm ECAL, HCAL with different absorbers and sampling non compensating But very expensive! particle Silicon-tungsten electromagnetic calorimeter: 1 cm 2 silicon pads 40 layers energy resolution E/E < 0.1/ E/GeV 0.01 0.1 ATLAS CDF GLAST CMS NOMAD AMS01 CDF LEP DO Silicon Area (m) 2000 m Required silicon: 1 3 10 3 m 2 Price today: 5 $/cm 2 Alternative design for electromagnetic calorimeter: Tile fibre calorimeter (lead scintillator) Challenge: Fibre readout in 4 T field Optimize light yield of fibres Hadron calorimeter Use same design & components Coarser segmentation Compensation (lead/scint. 4/1) Use stainless steel ( ) Coarser granularity e.g. 5 5 cm 2 Digital hadron calorimeter Alternative design for hadron calorimeter: Highly segmented 1 cm 2 pads Binary readout per RPC or small wire chambers Simple frontend electronics Precision measurements at Linear Collider high demands on detector performance LEP/SLC like detector not sufficient Summary Flavour tagging H cc Momentum resolution - e + e H Z H e + e ( + ) from lepton recoil mass - endpoint mass spectra in SUSY cascade Jet energy resolution - Higgs self-coupling HZZ - Multi-jet final states like ttH... World wide R&D projects started: TPC Europe, US, Canada (TPC Working group alephwww.mppmu.mpg.de/~settles/tpc/welcome3.html) Calorimeter Europe, Asia, US ( CALICE coll. polyww.in2p3.fr/tesla/calice_offic.html) Much more R&D effort needed! International Linear Collider Detector R&D committee Production of Higgs bosons Higgs-strahlung and WW-fusion: (ZZ H) = 1/10 (WW H ) Higgs-strahlung: detection of Higgs bosons independent of decay e + e HZ H e + e ( + ) Measurement of Higgs-strahlung and WW-fusion cross sections Determination of Higgs couplings to W- and Z-bosons g HWW and g HZZ e + e - physics: precise absolute measurements and theoretical predictions of cross sections 350 GeV 500 GeV Higgs mass measurement: Kinematic fit Energy scale determined by E beam 500 fb -1 e + e HZ bb qqe + e HZ bb l + l (Compare measurements of m W at LEP and Tevatron) m H 40 MeV (independent of m H ) Measurement of the total width H : Heavy Higgs (m H > 2 m Z ): broad Higgs because of H WW,ZZ direct measurement of H possible H / H 10% Light Higgs m H < 160 GeV Higgs is very narrow H < 10 MeV Measurement at LC through a) H WW from WW fusion b) BR(H WW) = H WW / H H / H 5% H (m H ) in the Standard Model: 2m W Determination of Higgs couplings: g HZZ 0,012 g HWW 0,012 g top 0,030 g bottom 0,022 g charm 0,037 g tau 0,033 Relative precision of Higgs couplings: ( m H = 120 GeV, 500 fb -1 ) Examples of other precision measurements Test of electroweak radiative corrections r W Top mass W couplings (TGC) 3 parameter (SM values): Measurement at threshold m t = 175 0,1 GeV 100 fb -1 m t 200 MeV Giga-Z: Production of 10 9 Z bosons 100-fold LEP I statistics Polarisation (like SLC) 30 fb -1 = 1/2 year Comparison SM fits 2001 and Giga-Z: Compare with directly measured Higgs mass