Detector for a Linear Collider 8th Topical Seminar on Innovative Particle and Radiation Detectors...
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Transcript of Detector for a Linear Collider 8th Topical Seminar on Innovative Particle and Radiation Detectors...
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 2001
• 35 MV/m s = 800 GeV already achieved with improved manufacturing (electropolishing)
Superconductive cavities
Acceleration gradient
23 MV/m s = 500 GeV
10.10.2002
800 GeV
Very recent result from 4 nine-cell modules:
B) Luminosity
pointn interactioat dimensions beamσ2)(factor t enhancemen disruption
frequency repetition pulsebunchper )(positrons electrons ofnumber
pulseper bunches ofnumber
)(
rep
e
b
yx
DHfNn
Strong focussing at the interaction point
Dyx
HfNn
L σσ4rep
2eb
nm5σnm550σ yx
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 (mH << s)
LC LEP II /10
Luminosity:
• LEP II L = 1032/cm2/s• LC L 1034/cm2/s
Higgs-factory: 100/fb/year = 1000 HZ/year
Giga-Z (s = mZ) 109 Z-bosons in 1/2 year
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 colliderthen precision tests at LEP & SLC
Physics at a 1 TeV e+e– - Linear Collider
Keep in mind:Linear Collider comes probably after major discoveries at LHC
• Higgs physics• Supersymmetry (SUSY)• Alternative Theories• Top-quark physics• Standard Model (Giga-Z)...
• Detection of Higgs Bosons independent of decay
e+ e– H Z H e+ e– (+ – )
Higgs branching ratios:
• Couplings to fermions: gf = mf /v
• Couplings to gauge bosons:
gHWW = 2 mW2/v
gHZZ = 2 mZ2/v
Determination of Higgs couplings:
Higgs physics:
Higgs-Strahlung
• Spin: Energy scan at threshold (e.g. 3 points, 20 fb-1, 1/2 year)
Determination of the quantum number of the Higgs:
SM: JPC =0++
• Parity: Angular distribution (continuum) Discriminate SM Higgs and 0–+ -boson A
Verification of Higgs potential:
0λ0μλμ)(V 2422
4322 λH4
1HλHλ)H(V vv
vmH 2λ H
H
H
H H
HH
gHHH gHHHH
• Measurement of double Higgs strahlung e+ e– HHZ:
gHHH/ gHHH = 0.22
• Measurement of gHHHH not possible
λμ- n valueexpectatio Vacuum 2v
Comparison of Higgs physics e+ e– linear collider and LHC:
mH = 120 160 GeV
LHC 2300 fb-1
X/X
LC 500 fb-1
X/X
mH 10-3 310-4
H ---- 0.04 0.06 gu-type ---- 0.02 0.04 gd-type ---- 0.01 0.02 gHWW ---- 0.01 0.03 gtop/gHWW 0.070 0.023 gHZZ/gHWW 0.050 0.022 CP Test ---- 0.03 gHHH ---- 0.22
Linear collider will be in Higgs physicswhat LEP was in W- and Z-physics
Supersymmetry:
If mSUSY < 2 TeV discovery at the LHC
Possible particle spectra:
Advantage of Electron-Positron-Collider:• Mass measurements by energy scans at kinematic threshold • Polarisation of electrons (and possibly positrons)
Separation of SUSY partners, e.g.:
• Skalar partners of fermions
• Fermionic partners of bosons
• 2 Higgs doublets
g~,χ~,,χ~,χ~ 04
01
HA,H,h,
SUSY will be new Standard Model
21 t~,t~,,μ~,μ~,e~,e~ LRLR
RRRRLLLL e~e~ee e~e~ee
Detector R&D for an e+ e– - Linear Collider:
• Higher particle energies from GeV to TeV
• More complex final states e+ e– ZHH 6 jets/leptons e+ e– H+H– tb tb 8 jets
• Resolution e+ e– ZH e+ e– (+ – ) + X SUSY (missing energy)
• Accelerator background, luminosity, bunch separation
...we want to build the best apparatus...
Why new & improved e+ e– detector?
More differences to LEP
• Small cross section of signal two-photon background• Large Lorentz boost high particle density in jets, e.g. 1/mm2 in vertex detectorTrigger:(example TESLA)
• bunch trains 1 ms, • 5 Hz repetition rate• bunch separation 337 ns• but 199 ms between two trains
200 ms
1 ms
no hardware trigger
No dead time• Store data of whole train in front end• Software selection within 200 ms
Detector R&D for an e+ e– - Linear Collider:
World wide R&D effort started
Use most modern technology for best suited LC detector
I. Vertex detector III. CalorimeterII. Tracker
Here 3 examples:
I. Vertex detector
• Precise reconstruction of primary and secondary event vertices
• Identification of b- and c-quarks, - leptons in Higgs decays
Multi-layer pixel detectorTESLA SLD
Inner radius 15 mm 28 mm
Single point resolution < 5 m 8 m
Material per layer (X0) 0.06% X00.4% X0
Total material budget < 1% X0
Impact Parameter 300 m for > 3(independent of s)
Goal: reconstruction of primary vertex
(IP) < 5 m 10 m / (p sin3/2 )
SLD: 8 m 33 m / (p sin3/2 )
1. Material budget:
• Thin detectors 60 m (= 0.06% X0)• 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
(ri = 1.5 cm)
CMS
(ri = 4.3 cm)
Dose (,e–,h) 10 kGy 1000 kGy
Neutron flux 1010/cm2 1015/cm2
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/pt ) < 5 × 10-5 (GeV/c )-1 (full tracker)
Large Si-Tracker à la LHC experiments?• much lower particle rates at linear collider• keep material budget low
Large TPC • 1.7 m radius• 3% X0 barrel (30% X0 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 E×B effects)
- Only fast electron signal
- Intrinsic ion feedback suppression
GEM or Micromegas
Wires
GEM
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 104 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 coupling chevrons
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
EE %30
E%30E%60
Jet energy resolution:
W/Z identification by mass reconstruction in 4 jets: Include Fig 4.3.2 from TDRInclude Fig 4.3.2 from TDRInclude Fig 4.3.2 from TDRInclude Fig 4.3.2 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 clustersFrom energy flow to particle reconstruction!
Highly granular calorimeter:
Electromagnetic:• identify particles down to low energies• longitudinal segmentation X0
• X0/ small• transversal segmentation rM
• no cracks, magnet coil outside
Hadron calorimeter:
• cell size close to X0 • good cluster separation• good energy resolution
Si/W natural choice rM= 9 mm
ECAL, HCAL with different absorbers and sampling non compensatingECAL, HCAL with different absorbers and sampling non compensating
But very expensive!
particle
Silicon-tungsten electromagnetic calorimeter:
• 1 cm2 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 (m²)
100
1000
10
1
2000 m²
Required silicon: 1 – 3 103 m2
Price today: 5 $/cm2
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 cm2
Digital hadron calorimeter
Alternative design for hadron calorimeter:
• Highly segmented 1 cm2 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 committeehttp://blueox.uoregon.edu/~lc/randd.pdf