TESLA DetectorMarkus Schumacher, University of Bonn

American Linear Collider Workshop, Cornell, July 2003

Requirements

Basic Concepts

Developments

Requirements from Physics

momentum: (1/p) = 7 x 10-5/GeV (1/10xLEP) e+e-ZHllX goal: M<0.1x dominated by beamstrahlung

impact parameter: d=510/p(GeV)m (1/3xSLD) excellent flavour tagging capabilities for charm and bottom quarks e.g. measurement of Higgs branching ratios

jet energy : E/E = 0.3/E(GeV) (<1/2xLEP) MDijet ~ Z/W e.g. separation between e+e-WWqqqq and e+e-ZZqqqq

LC LEP

reconstruction of multijet final states: e.g. e+e-H+H- tbtb bqqb bqqb

hermetic down to 5 mrad missing energy topologies (e.g. SUSY and Higgs) Physics determines detector design

Requirements due to the accelerator design

Time Structure:

Event rates: Luminosity: 3.4x1034 cm-2 s-1 (6000xLEP)e+e-qq,WW,tt,HX 0.1 / train e+e-X:~200 /Train

Background from Beamstrahlung: 6x1010/BX 140000 e+e-/BX + secondary particles (n,)

950 µs 199 ms 950 µs

2820 bunches

5 Bunch Trains/s tbunch=337ns

But still: 600 hits/BX in Vtx detector 6 tracks/BX in TPC

E=12GeV/BX in calorimeters E 20TeV/BX in forward cals.

Large B field and shielding

High granularity of detectors and fast readout for stable pattern recognition and event reconstruction

Basic TESLA Detector Concept

No hardware trigger, dead time free continous readout for complete bunch train (1ms)

Zero suppression, hit recognition and digitisation in FE electronics

Large gaseous central tracking device (TPC)

High granularity calorimeters

High precision microvertex detector

All inside magnetic field of 4 Tesla

Overview of tracking system

Central region:Pixel vertex detector (VTX)Silicon strip detector (SIT)Time projection chamber (TPC)

Forward region: Silicon disks (FTD) Forward tracking chambers (FCH)(e.g. straw tubes, silicon strips)

Requirements:

•Efficient track reconstruction /good resolution down to small angles

•independent, robust track finding in TPC (200) and in VTX+SIT (7 points) allows calibration, alignment

•excellent momentum resolution (1/p) < 7 x 10-5 /GeV

Vertex Detector: Conceptual Design

5 Layer Silicon pixel detector

•Small R1: 15 mm (1/2 SLD)

•Pixel Size:20x20m2 Point =3 m

•Layer Thickness: <0.1%X0 suppression of conversions – ID of decay electrons minimize multiple scattering

800 million readout cells

Hit density: 0.03 /mm2 /BX at R=15mm pixel sensors

Read out at both ladder ends in layer 1: frequency 50 MHz, 2500 pixel rows complete readout in: 50s ~ 150BX

<1% occupancy no problem for track reconstruction expected

Impact parameterd ~R1 point

Vertex Detector: Technology OptionsEstablished Technology: CCDs

Excellent experience at SLD (300 million channels)

R&D: efficiency and stability of charge transfer readout speed, thinning of sensors,

mechanics, radiation hardness

„New“ Technologies: MAPS (Monolithtic Active Pixel Sensors), FAPS DEPFET (Depleted Field Effect Transistor)

HAPS (Hybrid Active Pixel Sensors),SiO

Each pixel can be adressed individually

Only single row active per ladder smaller power consumption

First amplification in pixel smaller noise

R&D: above + building of large devices

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See Chris‘ talk for more details

Flavour Tagging

•LEP-c

Powerful flavour tagging techniques (from SLD and LEP)

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e.g. vertex mass

charm-ID: improvement by factor 3 w.r.t SLD

Expected resolution in r,and r,z

~ 4.2 4.0/pT(GeV) m

Flavour Tagging : Recent Studies Inner layer at 1.5cm is very important, e.g. e+e-Z*ZH

ZHllbb, ZHllcc, ZHllgg

W/O inner layer: charm tagging degraded by 10%

Double layer thickness small effect

Quark Antiquark discrimination via Vertex/Dipole Charge: bottom: p= 80% = 80% charm: p= 90% 35%

However: minimal amount of material important

limited number of conversions, electron-id, reconstruction of vertex mass including 0, …

Gaseous or Silicon Central Tracking Detector?

gaseous silicon

Motivation for a TPC

Large no. of 3D space points robust and efficient track reconstruction in high track density environment

new heavy stable particles GMSB SUSY: + G~ ~

Minimal material little influence on calorimetry little multiple scattering small number of conversions

dE/dx particle identification Tracking up to large radii Reconstruction of V0, Kink Tracks

aid energy/particle flow + sensitivity to new physics

TPC Conceptual Design

Radial space points: 200

Point res.: < 140 m (goal:100 m)

Pad size: 6 (r) x 2 (phi) mm2

Large lever arm: RI/A = 40/160 cm

Little material: < 3% X0

Gas choice: Ar:CO2:CH4 = 93:2:5 % (CF4 also investigated) Compromise between drift velocity ~ 5cm/s and neutron cross section

Total Drift time 50 s = 160 BX 80000 hits in TPC (physics+BG)

8x108 readout cells (1.2MPads+20MHz) 0.1% occupancy

No problem for pattern recognition/track reconstruction

TPC: (1/p) = 2.0 x 10-4 GeV-1 +VTX: (1/p) = 0.7 x 10-4 GeV-1

Gas Electron Multipliers or MicroMEGAS

better instrinsic point resolution

• 2 dimensional readout symmetry

• electron signal read out

• Small hole separationreduced ExB effects

natural supression of ion feedback

no wire tension thin endplates

Gas Amplification & Point Resolution

- chevron pads- large number of small silicon pads - resistive or capacitive coupling of neighbouring pads - larger gap between GEMs and pad plane

Small width of electron cloud (single pad) improve point resolution by charge sharing

(details see Ron’s and Dean’s talks)

Intermediate and Forward Tracking

SIT: 2 Layers of Si-Strips r = 10m

FTD: 7 Disks 3 layers of Si-pixels 50x300m2

4 layers of Si-strips r= 90m

FCH: 4 LayersStrawtubes or Silicon strips (double sided)

Forward tracking (e.g. e+e-WW qqlrecover mom. resolution at small angles

250 GeV

Increase track matching from TPC to VTX by 4 %

Improve Momentum resolution: TPC+VTX: (1/p) = 0.7 x 10-4 GeV-1

V0-Reco. Eff. 73 86% (for r=6to11cm)

track reconstruction efficieny: =98.4 (incl. Background hits)

+SIT : (1/p) = 0.5 x 10-4 GeV-1

Calorimetry

ZHHqqbbbb

Kinematic fits often not applicable – Beamstr., ISR, , LSPIntrinsic jet energy resolution is of vital importance

Design optimised for Particle/Energy Flow Algorithm

• Excellent jet energy resolution much of LC physics depends

on reconstruction of invariant masses from jets in hadronic final states

• Good energy and angular resolution for photons

• Reconstruction of non-pointing photons

• Hermeticity

Requirements:

Particle / Energy Flow

60 % charged particles:30 % :10 %KL,nThe energy in a jet is:

Reconstruct 4-vectors of individual particles avoiding double counting

Charged particles in tracking chambersPhotons in the ECALNeutral hadrons in the HCAL (and possibly ECAL)

need to separate energy deposits from different particles

• small X0 and RMoliere : compact showers

• high lateral granularity D ~ O(RMoliere)

• large inner radius L and strong magnetic field

granularity more important than energy resolution

KL,n

e Discrimination between EM and hadronic showers

• small X0/had • longitudinal segmentation

Calorimeter Conceptual Design

ECAL and HCAL inside coil

large inner radius L= 170 cm good effective granularity

ECAL: silicon-tungsten (SiW) calorimeter (preferred choice)• Tungsten : X0 /had = 1/25, RMoliere ~ 9mm

(gaps between Tungsten increase effective RMoliere)• Lateral segmentation: 1cm2 matched to RMoliere

• Longitudinal segmentation: 40 layers (24 X0, 0.9had)

• Resolution: E/E = 0.11/E(GeV) 0.01

x~BL2/(RM D) 1/p

x distance between charged and neutral particle at ECAL entrance

2nd option: 45 layers of Pb(W)+scintillating plates+WLS

+ 3 layers of Si sensors (.9x.9 cmxcm)

Two Options:

Tile HCAL (Analogue readout)

Steel/Scintillator sandwich

WLS + Photodetectors (WLS: different geometries) (APDs, SiPM on tiles,…)

Lower lateral segmentation 5x5 to 25x25 cm2

• Longitudinal segmentation: 9-12 samples• 4.5 – 6.2 had (limited by coil radius)

Hadron Calorimeter

HCAL

ECAL

Digital HCAL (digital readout)

via RPCs,GEMS, small scint. tiles

High lateral segmentation 1x1 cm2

resolution: E/E =0.35/E(GeV) 0.03

seperation: fake=10-3

Calorimeter Reconstruction

`Tracking calorimeter’– very different from previous detectors

Requires new approach to reconstruction

Already a lot of excellent work on powerful particle/energy flow algorithms

Still room for new ideas/ approaches

A lot of R&D activities:

Continue evaluation of digital vs analog HCAL

Calorimeter segmentation, HCAL active medium

Simulation of hadronic showers test beams

jet energy:E/E = 0.3/E (GeV) = 68mrad/E(GeV) 8mrad without vertex constraint for photons

OPAL

Forward Calorimeters

LCAL: Beam diagnostics and fast luminosity (28 to 5 mrad) ~104 e+e— pairs/BX 20 TeV/BX 2MGy/yr Need radiation hard technology: SiW, Diamond/W Calorimeter or Scintillator Crystals

LAT: Luminosity measurement from Bhabhas (83 to 27 mrad) SiW Sampling Calorimeter

aim for L/L ~ 10-4 require = 1.4 rad

TDR version of mask L* = 3 m

Tasks:

Shielding against background

Hermeticity / veto

Recent Developments

• Shower leakage • Difficulty in control of inner acceptance to ~1m

TDR version of LAT difficult for a precision lumi measurement ?

New L* = 4-5 m version currently being studied. Flat: better for Lumi. measurement More Space for electronics etc. inner radius LAT: 8cm 5cm Hermetic to 3.9 mrad

(was 5.5 with gaps) less indirect background hits ??

Design in flux + very active R&D

Detector Optimization

Current detector concept essentially unchanged from TDR

+ OTHER/NEW IDEAS……

Time to think again about optimizing detector design, consider the detector as a whole entity

Optimize design w.r.t. overall detector performance using key physics processes, e.g.

Need unbiased comparison• Same/very similar reconstruction algorithms• Common reconstruction framework • Same Monte Carlo events

looking at TPC length, extra Si tracker between TPC and ECAL,…

something forgotten ? devil’s advocate committee

Conclusions

Precision physics determines the detector design

Basic design almost unchanged compared to TDR

Proof of principle for the best suited technologies to be provided by ongoing R&D

Optimise Overall Detector Performance in worldwide collaboration to find best detector concept for a future linear collider !

The Physics potential at a LC is excellent, the requirements to the detector are challenging

High lumi large statistics small systematics need best detector which can be build