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Particle Detectors for Colliders Calorimeters. Robert S. Orr University of Toronto. Generic Detector. Layers of Detector Systems around Collision Point. R.S. Orr 2009 TRIUMF Summer Institute. Scintillators. charged particle. photons. atom molecule lattice.

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Particle detectors for colliders calorimeters

Particle Detectors for CollidersCalorimeters

Robert S. Orr

University of Toronto


Generic Detector

  • Layers of Detector Systems around Collision Point

R.S. Orr 2009 TRIUMF Summer Institute


Scintillators

charged particle

photons

  • atom

  • molecule

  • lattice

  • Charged particle passing through matter distorts

  • Relaxation of distortion – light emitted

Successive

excitation & emission

– different λphotons

  • Emitted photon may – excite another molecule

eachstep

whole chain

  • Very fast – good timing resolution


~ 100 photoelectrons per cm.

  • Spatial resolution ~ size of scintillator ~10s cm

Scintillating fibres

R.S. Orr 2009 TRIUMF Summer Institute


Why are scintillators transparent to emitted light?

  • Stokes shift

R.S. Orr 2009 TRIUMF Summer Institute


Wavelength Shifting

R.S. Orr 2009 TRIUMF Summer Institute


Photomultiplier

number of stages

  • Fast

  • Low noise

  • High gain

R.S. Orr 2009 TRIUMF Summer Institute


PM Sensitivity

R.S. Orr 2009 TRIUMF Summer Institute


Modern Photodetectors

  • Micro-channel plates

  • Multi-anode pm

  • Hybrid pm

  • Visible light photon counters

R.S. Orr 2009 TRIUMF Summer Institute


Electromagnetic Showers

Number of particles after

Average energy

At the critical energy

assume this is max depth

incident

Converts to 2 electrons

shower grows as ln E

linear energy measurement

Each electrons will have emitted a brems photon of energy

resolution improves with energy

Now have 4 particles energy

R.S. Orr 2009 TRIUMF Summer Institute


Monte Carlo Simulation of an EM Shower

Calc

Put b=0.5

Get a from

R.S. Orr 2009 TRIUMF Summer Institute


“b” is sort of material independent

R.S. Orr 2009 TRIUMF Summer Institute


Transverse Shower Profile

  • Shower Broadens as it develops

    • Pair

    • Brems

    • Compton

    • Multiple Coulomb

  • Shower Broadens as it develops

    • dense central core

    • spreading with depth

  • Moliére Radius

  • Like radiation length, Moliére radius scales for different materials

  • In terms of Moliére radius, shower width is roughly independent of material - 90% of energy in

R.S. Orr 2009 TRIUMF Summer Institute


Comparison of Hadronic & Electromagnetic Showers

R.S. Orr 2009 TRIUMF Summer Institute


Hadronic Calorimeters

  • Strong (nuclear) interaction cascade

  • Similar to EM shower

hadronic interaction length

  • Energy Resolution

  • shower fluctuations

  • leakage of energy

hadronic calorimeter

nearly always sampling calorimeters

  • invisible energy loss mechanisms

  • Shower length

R.S. Orr 2009 TRIUMF Summer Institute


Sampling Calorimeter

R.S. Orr 2009 TRIUMF Summer Institute


Hadronic Lateral Shower Profile

  • Hadronic shower much broader than EM

Fe

  • Mean hadronic versus MCS

Fe

R.S. Orr 2009 TRIUMF Summer Institute


Hadronic Shower Longitudinal Development

ZEUS

Uranium/Scint

R.S. Orr 2009 TRIUMF Summer Institute


Lateral Scaling with Material

90% containment does not scale

core scales

R.S. Orr 2009 TRIUMF Summer Institute


Calorimeter Energy Resolution

sampling and shower fluctuations

energy

number of samples

energy deposited in a sampling step

stochastic term

R.S. Orr 2009 TRIUMF Summer Institute


Calorimeter Energy Resolution

e.g. # of photo-electrons in PM, ion pairs in liquid argon

counting statics in sensor system

mean # of photo-electrons in PM per unit of incident energy

this term is usually negligible

shower leakage fluctuations – make calorimeter as deep as $$ allow

R.S. Orr 2009 TRIUMF Summer Institute


Calorimeter Energy Resolution

  • important for low level signal

  • liquid argon electronics

  • detector capacitance

noise - detector or electronics

N channels with some intrinsic noise

noise (energy)

deposited energy

behaviour

increases with number of channels summed over

R.S. Orr 2009 TRIUMF Summer Institute


Calorimeter Energy Resolution

  • constant in E

inter - calibration uncertainty of channels

  • fractional channel to channel gain uncertainty

  • spatial in-homogeneity of detector energy response

  • dead space

  • temperature variation

  • radiation damage

  • all these influence spatial variation of effective energy response

constant

R.S. Orr 2009 TRIUMF Summer Institute


Calorimeter non-uniformity

R.S. Orr 2009 TRIUMF Summer Institute


Generic Detector

  • Layers of Detector Systems around Collision Point

R.S. Orr 2009 TRIUMF Summer Institute


Semi-empirical model of hadron shower development

hadronic part

electromagnetic part

radiation length

interaction length

- significant amount of material in front of calorimeter (magnet coil etc.)

R.S. Orr 2009 TRIUMF Summer Institute


More Rules of Thumb for the Hobbyist

  • Mixtures in sampling calorimeters

  • Shower maximum

active + passive material

  • 95% Longitudinal containment

  • 95% Lateral containment

R.S. Orr 2009 TRIUMF Summer Institute


Typical Calorimeter Resolutions

  • Homogeneous EM (crystal, glass)

CLEO, Crystal Ball, Belle, CMS.....

  • Sampling EM (Pb/Scint, Pb/LAr)

CDF, ZEUS, ALEPH, ATLAS.....

  • Non-compensating HAD (Fe/Scint, Fe/LAr)

CDF,ATLAS,H1, LEP = everyone

  • Compensating HAD (DU/Scint)

ZEUS, HELIOS

R.S. Orr 2009 TRIUMF Summer Institute


Invisible Energy in Hadronic Showers

R.S. Orr 2009 TRIUMF Summer Institute


Difference in Response to Electrons and Hadrons

R.S. Orr 2009 TRIUMF Summer Institute


Effect of e/h on Energy Resolution

Resolution tail

Fe/Scint

DU/Scint

R.S. Orr 2009 TRIUMF Summer Institute


Effect of e/h on Linearity

Fe/Scint

DU/Scint

R.S. Orr 2009 TRIUMF Summer Institute



Weighting to Correct for e/h

Energy resolution does not improve

Weight down EM part of shower

tune

R.S. Orr 2009 TRIUMF Summer Institute


Jet Energy Resolution

Jet-jet Mass Resolution

Fluctuations between EM and Hadronic component in jets will degrade the energy resolution for jets

Effects other than e/h dominate the 2-jet mass resoluton

R.S. Orr 2009 TRIUMF Summer Institute


Jet-Jet Mass Resolutions

R.S. Orr 2009 TRIUMF Summer Institute


Conceptual Readout Schemes

R.S. Orr 2009 TRIUMF Summer Institute


ZEUS Forward Calorimeter

R.S. Orr 2009 TRIUMF Summer Institute



Generic Detector

  • Layers of Detector Systems around Collision Point

R.S. Orr 2009 TRIUMF Summer Institute


LArCalorimetry

  • Five different detector technologies

  • Calorimetry coverage to

SM Higgs Discovery Potential

EM Calorimeter

Hadronic & Forward

Calorimeters

EM Calorimeter

WW Fusion

Tag jets in Forward Cal


LAr Calorimeter Technology Overview

  • Design Goals Technology

    • EM Calorimeters ( ) and Presampler ( )

    • Hadronic Endcap ( )

    • Forward Calorimeter ( )

Lead/Copper-Kapton/Liquid Argon Accordion Structure

Copper/Copper-Kapton/Liquid Argon Plate Structure

Tungsten/Copper/Liquid Argon Paraxial RodStructure


LAr and Tile Calorimeters

Tile barrel

Tile extended barrel

LAr hadronic

end-cap (HEC)

LAr EM end-cap (EMEC)

LAr EM barrel

LAr forward calorimeter (FCAL)


Electromagnetic Barrel

Barrel Module Schematic

with presampler

Half Barrel Assembly

  • 2x16 modules

  • I.R/O.R 1470/2000 mm

  • 22 - 33

  • 3 longitudinal samples

  • presampler

  • 64 gaps /module

  • 2.1 mm gap

  • 2x3100 mm long

R.S. Orr 2009 TRIUMF Summer Institute


Electromagnetic Endcap

  • 2x8 modules

  • Diam. 4000 mm

  • 22 - 37

  • 3 longitudinal samples

  • Front sampling of 6

  • for ,  - strips.

  • 96 gaps /module outer wheel

  • 32 gaps/module inner wheel

  • 2.8 - 0.9 mm gap outer

  • 3.1-1.8 mm inner

R.S. Orr 2009 TRIUMF Summer Institute


AccordionStructure

Pb Absorber

  • Honeycomb spacer

  • &

  • Cu/Kapton electrode

R.S. Orr 2009 TRIUMF Summer Institute


Prototype of EM endcap

Detail of Kaptons

R.S. Orr 2009 TRIUMF Summer Institute


ATLAS FCAL

R.S. Orr 2009 TRIUMF Summer Institute



LAr Forward Calorimeters

  • FCAL C assembly into tube – Fall 2003


ATLAS HEC Structure

R.S. Orr 2009 TRIUMF Summer Institute


Hadronic Endcap Calorimeter (HEC)

Front Wheel

Rear Wheel

Wheel Assembly

Composed of 2 wheels per end

Front wheel: 67 t 25 mm Cu plates

Back wheel: 90 t 50 mm Cu plates







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