Precision Tracking COLLID04 Novosibirsk May 2004 Joachim Mnich

Precision Tracking at future colliders LHC: Large Silicon TrackerLC: A Novel Time Projection Chamber ATLAS CMS Detector for TESLA

The Large Hadron Collider (LHC) at CERN(Geneva) protons Atlas CMS ATLAS pp-collisions at very high energy (2  7 TeV) and luminosity /cm 2 /s

Tracking at the LHC LHC physics programme  Higgs  SUSY and New Physics searches  Test of the Standard Model + heavy ion Challenges for tracker  LHC 25 ns bunch crossing rate  fast detector response   20 pp interactions  1000 tracks/bx  high granularity  Resistance to high radiation  Tracking with silicon detectors  Vertex: layers of pixel detectors  Main tracker: large area silicon strip detectors + transition radiation detector (ATLAS) straw tubes & radiator Examples:  H  ZZ  4   H   4 jets  tt  bb + 2 jets + l l l Atlas: bb + 22 min. bias events

5.4 m Outer Barrel –TOB- Inner Barrel –TIB- Endcap –TEC- Pixel 2,4 m Inner Disks –TID- ATLAS: Hybrid pixel detectors 3 layers Silicon strip detector (SCT) 4 layers in barrel 9 layers in endcap all layers 2 stereo detectors Transisiton Radiation Tracker straw tubes + radiator (36 points) All in a 2 Tesla solenoid Design Comparison CMS: All silicon tracker Hybrid pixel detectors 3 layers Silicon strip detectors 10 layers in barrel 9 layers in endcap All in a 4 Tesla solenoid

Radiation Hardness Expected radiation doses Pixel vertex detectors per year  3  n/cm 2 (1 MeV equiv.)  150 kGy charged particles Strip detectors in 10 years  1.5  n/cm 2  60 kGy Effects on silicon sensors Creation of impurities Change of depletion voltage  type inversion Increase of dark current Increase of oxide charges  strip/pixel capacitance Effects on readout chips Change of MOS structures Change of amplification Single event upset (bit flip)

Radiation Hardness Radiation hard sensors: Operate at low temperature (  –10°C)  increases time constant of reverse annealing to many years  reduces dark current & avoids thermal runaway Use crystal orientation reduces charge trapping at Si/SiO 2 boundaries Radiation hard chips: Deep sub-micron technology 0.25  m structures  Small oxide structres  intrinsically radiation hard  Industrial standard  cheap  DMILL technology relies on high quality oxide annealing reverse annealing

Vertex Detectors Hybrid pixel detectors Active silicon sensor Bump-bonded to readout chip  parallel readout & processing required for 40 MHz bunch crossing CMS General detector layout:

Pixel detectors:ATLASCMS # layer barrel endcap radii [cm]5/10/124/7/10 pixel size [  m 2 ]50  300/  150 # channels 8   10 7 sensitive area [m 2 ]21.1 Vertex Detectors Comparison of parameters:  area of LEP vertex detectors

CMS readout chip Status of Pixel Detectors R&D finished Prototyping: Testbeam: ATLAS CMS sensor in 25 ns beam at LHC hit rates of 80 MHz/cm 2

Silicon Strip Detectors At larger radius no pixel detector possible (# of readout channels) pixel  0.1  0.1 mm 2  strip  0.1  100 mm ATLAS CDF GLAST CMS NOMAD AMS01 CDF LEP DO Silicon Area (m²) Silicon strip det.:ATLASCMS # layer barrel endcap 4 stereo 9 stereo 10 (4 stereo) 9 (33% stereo) # modules 2  # channels 6   10 6 silicon area [m 2 ]61206 Largest silicon detectors ever build! CMS ATLAS

Example of modules: CMS outer barrel ATLAS endcap Silicon Strip Detectors

Mass production of modules has started Use robots to assemble thousands of modules to O(20  m) precision Production of Silicon Strip Detectors CMS

Part of the CMS barrel carbon fiber support structure Integration of Modules & Construction of Tracker Support structure for the ATLAS barrel tracker

Expected Performance of LHC Trackers p T resolution transverse impact parameter  (IP T )  10  m Example CMS: For high momentum tracks:  (p T )/p T  1.5  p T /GeV (  =0)

Example: expected b-jet tagging with CMS Physics Performance of LHC Trackers

ATLAS Transition Radiation Tracker Bonus: electron/pion separation Two threshold analysis 5.5 keV 0.2 keV B d 0  J/ψ K s 0 ~1 TR hit ~7 TR hits

Large scale silicon tracker à la CMS have large material budget Support, cooling, electronics, cables etc. Active silicon contributes only marginally  Degradation of calorimeter performance  Disadvantage compared to a gaseous trackers (TPC, jet chamber,...) Active silicon CMS The back side of the medal: Example: CMS full silicon tracker LHC Tracker

Summary LHC Tracker (ATLAS & CMS) LHC enviroment requires fast, radiation hard detectors  Choice of large silicon (pixel & detectors) (+ straw tubes at larger radii) Largest silicon detectors ever build Detectors under construction are adequate for the LHC physics programm - High resolution on momentum and secondary vertices - Can cope with hostile conditions at the LHC high muliplicity and extreme radiation doses

e + e – - Linear Collider A Linear Collider with Energy in the TeV range High luminosity (> /cm 2 /s) is the next large international HEP project Concepts: Superconducting cavities: TESLA (Europe, DESY et al.) Warm cavities: NLC (America) and GLC (Asia) Drive beams: CLIC (CERN) route to multi-TeV energies

Comparison of physics at LC and LHC LHC discovery machine for Higgs & SUSY LC precison measurements cf. discovery of W- and Z-bosons at hadron collider followed by precision tests at LEP & SLC Physics at a 1 TeV e + e – - Linear Collider Example: Study of Higgs properties e + e –  H Z  H e + e – (  +  – )  Tag Higgs through leptonic Z decay (recoil mass)  Study Higgs production independent of Higgs decay  1000 events/year

 Momentum resolution (full tracker)  (1/p t ) < 5  GeV -1 Higgs Physics at the Linear Collider  Couplings to fermions: g f = m f /v  Couplings to gauge bosons: g HWW = 2 m W 2 /v g HZZ = 2 m Z 2 /v  Best possible vertex detector to distinguish b- and c-quarks Determine Higgs branching ratios: ideally: recoil mass resolution only limited by Z width

Main difference for detector design between cold and warm machines timing of bunches TESLAGLC/NLC bunch intervall337 ns1.4 ns # bunches/train bunch length 950  s0.27  s repetition rate5 Hz100 – 150 Hz TESLA: higher readout speed to limit occupancy (several readout cycles per bunch train) GLC/NLC: bunch separation is more difficult 2820 bunches  t = 337 ns 199 ms time TESLA 192 bunches  t = 1.4 ns 7-10 ms time GLC/NLC Tracking at the Linear Collider

Vertex Detector Goal (TESLA TDR) reconstruction of primary vertex to  (PV) < 5  m  10  m / (p sin 3/2  )  cf: SLD 8  m  33  m / (p sin 3/2  )  Multi-layer pixel detector Stand alone tracking Internal calibration Small pixel (20  m  20  m) 800 million channel TESLA SLD Inner radius15 mm 28 mm Single point resolution < 5  m 8  m Material per layer (X 0 )0.06% 0.4% Total material budget< 1% X 0

Three main issues: I. Material budget Very thin detectors  60  m (= 0.06% X 0 ) of silicon No electronics in central part, i.e. no hybrid design Minimise support II. Radiation hardness High background from beam-strahlung and beam halo Much less critical than LHC But much more important than at LEP/SLC 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

III. 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 (TESLA) CCD design  Use column parallel readout CCD classic CP CCD Vertex Detector

Vertex Detector Technology Several technologies under study Examples:  Charge Coupled Device: Classical technology Create signal in 20  m active layer etching of bulk  total thickness  60  m Coordinate precision 2-5  m Low power consumption  DEPFET (DEPleted Field Effect Transistor) Fully depleted sensor with integrated pre-amplifier Low noise  10 e – at room temperature! Prototype (Bonn): 50  m × 50  m pixel 9  m resolution

Standard CMOS wafer integrating all functions i.e. no connections like bump bonds Very small pixel size achievable Radiation hardness proven Power consumption is an issue Pulse power?  MAPS (CMOS Monolithic Active Pixel Detectors) Vertex Detector Technology

Large Si-Tracker à la LHC experiments? Much lower particle rates at Linear Collider Keep material budget low  Large Time Projection Chamber 1.7 m radius 3% X 0 barrel (30% X 0 endcap) High magnetic field (4 Tesla) Goals  (1/p t ) < 5  GeV points (3-dim.) per track 100  m single point resolution dE/dx 5% resolution  10 times better single point resolution than at LEP Main Tracker Simulation of one TESLA bunch train background (beam strahlung) + 1 Higgs

New concept for gas amplification at the end flanges: Replace proportional wires with Micro Pattern Gas Detectors - Finer dimensions - Two-dimensional symmetry (no E×B effects) - Only fast electron signal - Intrinsic ion feedback suppression GEM or Micromegas Wires GEM Time Projection Chamber

Gas Electron Multiplier (GEM) (F. Sauli 1996) 140  m Ø 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 For TPC 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

Detection of electron signal from MPGD: no signal broadening by induction  short & narrow signals If 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 Micro Pattern Gas Detectors

Carlton/Victoria DESY/Hamburg Karlsruhe Orsay/Saclay R&D Work on TPC Aachen Triple GEM structure Examples

DESY Short & narrow pulses Examples of first results from triple GEM structures in high magnetic field Low ion feedback 2  Single point resolution O(100  m) R&D Work on TPC

Summary & Conclusions Tracking at the LHC: Large & precise tracking detectors mainly based on silicon technology under construction Hybrid pixel vertex detectors Start of data taking in 2007 Electron-Positron Linear Collider: Vertexing with ultrafine & fast silicon pixel detectors Tracking with high precision TPC exploiting micropattern gas detectors Worldwide R&D programs ongoing