Optimising a Detector from the Tracking Point-of-View

Palaiseau, 13/1/ 200Palaiseau, 13/1/ 20055

P. Colas - Optimising trackingP. Colas - Optimising tracking 11

Optimising a Detector Optimising a Detector from the Tracking Point-from the Tracking Point-of-Viewof-ViewP.Colas, CEA SaclayP.Colas, CEA Saclay

Optimisation : trade-off between constraintsconstraints to help the detector to fulfill its rolerole best



THE ROLE OF THE TRACKINGTHE ROLE OF THE TRACKING

Reconstruct verticesReconstruct vertices Enough accuracy to separate b from cEnough accuracy to separate b from c Determine vertex chargeDetermine vertex charge Reconstruct most of V°sReconstruct most of V°s

Measure charged tracksMeasure charged tracks High efficiency down to low angles and momenta, High efficiency down to low angles and momenta,

even for close tracks, for particle floweven for close tracks, for particle flow High accuracy to tell the charge at highest momentaHigh accuracy to tell the charge at highest momenta If possible, identify particle (e,If possible, identify particle (e,,,,K,free quark,…),K,free quark,…)



Linear Collider SpecificityLinear Collider Specificity

Physics requirementsPhysics requirements Flavour tagging by vertex findingFlavour tagging by vertex finding Higgs recoil mass (ZH->Higgs recoil mass (ZH-> anything) anything) Multijet final states : two-track separationMultijet final states : two-track separation Missing energy measurement : hermeticityMissing energy measurement : hermeticity Processes peaked at low angle : good coverageProcesses peaked at low angle : good coverage

EnvironmentEnvironment Backgrounds: muons, photons, neutrons : go 3D, go Backgrounds: muons, photons, neutrons : go 3D, go

high segmentationhigh segmentation



PHYSICSPHYSICS



Magnetic fieldMagnetic field

Roles: Roles: Curve tracks for p measurmnt Curve tracks for p measurmnt

ppTT/p/pTT=8=8/0.3Bl/0.3Bl22

Curve tracks to separate Curve tracks to separate charged from neutrals charged from neutrals (particle flow)(particle flow)

Background confinementBackground confinement ParametersParameters

Radius (transportation, cost), Radius (transportation, cost), lengthlength

Field intensityField intensity HomogeneityHomogeneity

Mask

B field

(See talk by F. Kircher)



BackgroundsBackgrounds

Effect of the beam Effect of the beam crossing angle crossing angle (K.Bü(K.Büer, SLAC MDI meeting, er, SLAC MDI meeting, 5 jan 2005)5 jan 2005)

Head-on ? 2mrad? Head-on ? 2mrad? 20 mrad? Small/large 20 mrad? Small/large hole?hole?

Input from the Input from the detector to the detector to the machine design!machine design!

TPC

VxDet

VxDet



Backgrounds : neutronsBackgrounds : neutrons

Impacts the aging of the Impacts the aging of the siliconsilicon

Causes occupation in the Causes occupation in the TPC, especially if the gas TPC, especially if the gas contains Hydrogencontains Hydrogen



TECHNOLOGYTECHNOLOGY

See talks by S. Aplin See talks by S. Aplin and T. Greenshawand T. Greenshaw

Digital TPC?Digital TPC? Could be used at an Could be used at an

intermediate radius intermediate radius between the vertex between the vertex detector and a standard detector and a standard TPCTPC

STANDARD TPC

DIGITAL TPC

Vx Det



GEOMETRYGEOMETRY

What must be the radius of the What must be the radius of the TPC? Trading size (RTPC? Trading size (R22) against ) against sagitta accuracy / B has a limit : sagitta accuracy / B has a limit : VV00s must be contained.s must be contained.

Up to which R do we need Up to which R do we need Silicon? Where from do we start Silicon? Where from do we start gas?gas?

Limit on the number of silicon Limit on the number of silicon layers fixed by the multiple layers fixed by the multiple scattering. About 5 for 300 scattering. About 5 for 300 micron wafers, more if layers are micron wafers, more if layers are thinner. thinner.



LOW ANGLE COVERAGELOW ANGLE COVERAGE

L has to be finite. A L has to be finite. A special device is special device is needed to cover low needed to cover low angles (K. Moenig) angles (K. Moenig)

(deg.)

A extended silicon envelope would allow TPC syst. to be corrected (A. Savoy-Navarro). But would not a few % of the surface be enough? Would the first layer of the calorimeter play this role?



Momentum resolution

pt (GeV/c)

10 100 1000

sig

ma

(1/p

t)

(10-4

Ge

V/c

-1)

1

2

3

4

5

2 x 74 x 8 4 x 14

An example : pad size in An example : pad size in the TPC, momentum the TPC, momentum resol°resol°

Depends on Depends on details of the details of the design: gas, design: gas, technology, technology, electronicselectronics

What is What is acceptable? Twice acceptable? Twice the cost for half the cost for half the resolution?the resolution?

BON COURAGE BON COURAGE

TESLA TDR Goal

D. Karlen

Pad dimensions (mm x mm)



COST ISSUESCOST ISSUES

trade-off running time / resolution (trade-off running time / resolution (//N), N), N ~ time ~ money) N ~ time ~ money)

trade-off reliability / price of componentstrade-off reliability / price of components trade-off multi-technology / scale effecttrade-off multi-technology / scale effect



BENCHMARKSBENCHMARKSProcessProcess Tested itemTested item

AAFBFB ++-- Charge Charge separationseparation

ZH -> ZH -> ++- - XX Recoil mass Recoil mass resolutionresolution

Bhabha Bhabha acolinearity, WW acolinearity, WW with W-> with W->

Low-angle Low-angle coveragecoverage

H branching H branching ratiosratios

Vertex finding, b/c Vertex finding, b/c discriminationdiscrimination

(see M. Battaglia’s talk)



CONCLUSIONSCONCLUSIONS

A lot has been done already to optimize the tracking, but:

x Technology evolution might lead us to revise some choices

x Need to be realistic in supports / cables / services

Benchmarks with realistic simulation and various options are strongly needed.

Optimising a Detector from the Tracking Point-of-View

Documents

vertex detector

greenshawdigital tpc

angle coverageh

low angles

particle flowhigh accuracy

sagitta accuracy b

3bl2curve tracks

close tracks