particle detectors for colliders calorimeters

Particle Detectors for Colliders

Calorimeters

Robert S. Orr

University of Toronto

R.S. Orr 2009 TRIUMF Summer Institute

Layers of Detector Systems around Collision Point

Generic Detector

Scintillatorscharged particle

photons

• Charged particle passing through matter distorts

• atom• molecule• lattice

• Relaxation of distortion – light emitted

* p A p A* A A

• Emitted photon may – excite another molecule Successive excitation & emission – different λ photons

*

*

*

* *

*

B

p p

B A

C BB

C

A

A

C

C

A

each step ~ 100 ps

whole chain ~ 1 10 ns

• Very fast – good timing resolution


• Can be extremely efficient ~ 2 /dE

MeV cmdx

2 4

collection efficiency

photomultiplier efficiency

1 /10 lost 10 /

eV cm

~ 100 photoelectrons per cm.

• Spatial resolution ~ size of scintillator ~10s cm 10

Scintillating fibres


Why are scintillators transparent to emitted light?

• Stokes shift


Wavelength Shifting


Gain = secondary emission factor N

dkV

number of stages

771 electron x

1110

00

1

nsG mA

50 50 mV

• Fast• Low noise• High gain

Photomultiplier


PM Sensitivity


Modern Photodetectors

V

photocathode

focusing electrodes

siliconsensor

electron

• Micro-channel plates• Multi-anode pm• Hybrid pm• Visible light photon counters


Electromagnetic Showers

incident 0

0E

Converts to 2 electrons 0

2e

EE

0~ 2

Each electrons will have emitted a brems photon of energy 0

4 E

E

Now have 4 particles energy 0

4

E

Number of particles after 0t 2 tN

Average energy 0

2 t

EE t

0maxmax

2 t Ct

EE EAt the critical energy

0max

ln

ln 2 cE E

t

assume this is max depth

max 0~ lnt E

0max

c

EN

E

max 0N E

~ ~ E N E

shower grows as ln E

linear energy measurement

resolution improves with energy


Monte Carlo Simulation of an EM Shower

1

0

a btt edEE

b

dt

b

a max

11.0 ln

i

at y C

b

max 0~ lnt E

Cy E E 0.5 , 0.5 iC e

Calc max ln it y C

Put b=0.5

Get a from max

1

at

b

dE

dt


“b” is sort of material independent


Transverse Shower Profile• Shower Broadens as it develops

• Pair

• Brems

• Compton

• Multiple Coulomb

• Moliére Radius 0S

MC

ER

E

2 421.2S eE m c MeV

• 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

• Shower Broadens as it develops

• dense central core

• spreading with depth

2 MR


Comparison of Hadronic & Electromagnetic Showers


Hadronic Calorimeters

• Strong (nuclear) interaction cascade• Similar to EM shower

2 1 30 35IEM had g cm A

hadronic interaction length

• Shower length

0I

hadronic calorimeternearly always sampling calorimeters

~ 5 ~ 4 @100

~ 13 ~ 10 @1

m GeV

m TeV

• Energy Resolution

• leakage of energy

• shower fluctuations

• invisible energy loss mechanisms


Sampling Calorimeter


Hadronic Lateral Shower Profile

Fe• Hadronic shower much broader than EM

• Mean hadronic versus MCS

Tp

0

16

1.8I cm

cm

Fe


Hadronic Shower Longitudinal Development

ZEUSUranium/Scint


Lateral Scaling with Material

90% containment does not scale

core scales


Calorimeter Energy Resolution

22 22

20 312 4ln

A A NAA E A

E EE E

0A

Esampling and shower fluctuations

EN

E

number of samplesenergy

energy deposited in a sampling step

E N E N E

E EN

E E

E E

E E

stochastic term 0 ~A E



22 22

20 312 4ln

A A NAA E A

E EE E

counting statics in sensor system

this term is usually negligible

1A

E

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

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

N n E

NE

N n E

n n n

1 1E

E n E

1

1A

n

2A shower leakage fluctuations – make calorimeter as deep as $$ allow



22 22

20 312 4ln

A A NAA E A

E EE E

noise - detector or electronics

increases with number of channels summed over

- important for low level signal- liquid argon electronics- detector capacitance

N channels with some intrinsic noise

3A

N E noise (energy)

E EN

E E

deposited energy1

Ebehaviour

3A E N



22 22

20 312 4ln

A A NAA E A

E EE E

inter - calibration uncertainty of channels

constant

- constant in E

• spatial in-homogeneity of detector energy response

4A

• fractional channel to channel gain uncertainty

• dead space

• temperature variation

• radiation damage

• all these influence spatial variation of effective energy response

E

k E

kE


Calorimeter non-uniformity



Generic Detector


Semi-empirical model of hadron shower development

radiation length

hadronic part

11

1E Hx

E

y

INC INCH

dEE E

dS

y eC

Cx e

electromagnetic part

0

0

0

E

H

S Sx

S Sy

interaction length

0.62 0.32ln

0.91 0.02ln

0.22

0.46

H E

H

E

E

E

C

0 0S - significant amount of material in front of calorimeter (magnet coil etc.)


More Rules of Thumb for the Hobbyist

• Shower maximum

max ~ 0.2 ln 0.7t E GeV

• 95% Longitudinal containment

95% max~ 2.5 ATTL t

0.13

ATT E GeV

• 95% Lateral containment

95% ~ 1R

• Mixtures in sampling calorimeters

active + passive material

0

0

0

1 ii

ieff

actact

act pass

crit criteff i

i iieff

crit actvis act

act critinc eff eff

f

mf

m m

f

Ef

E


Typical Calorimeter Resolutions

• Homogeneous EM (crystal, glass)

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

0.5% 3.0%0.5%

E E

• Sampling EM (Pb/Scint, Pb/LAr)8% 15%

1%E E

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

• Non-compensating HAD (Fe/Scint, Fe/LAr)70% 110%

5%E E

CDF,ATLAS,H1, LEP = everyone

• Compensating HAD (DU/Scint)35%

1%E

ZEUS, HELIOS


Invisible Energy in Hadronic Showers


Difference in Response to Electrons and Hadrons


Effect of e/h on Energy Resolution

Fe/Scint

DU/Scint

E E constE

Resolution tail


Effect of e/h on Linearity

DU/Scint

Fe/Scint


Weighting to Correct for e/h

Energy resolution does not improve

1

E1

e

h

Weight down EM part of shower

1e

h

' 1k k kE E c E

tune


Jet Energy Resolution

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

Jet-jet Mass Resolution

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


Jet-Jet Mass Resolutions


Conceptual Readout Schemes


ZEUS Forward Calorimeter



Generic Detector

LAr Calorimetry

SM Higgs Discovery Potential

• Five different detector technologies• Calorimetry coverage to

η 5

EM Calorimeter

WW FusionTag jets in Forward Cal

H

EM Calorimeter4H l

Hadronic & ForwardCalorimeters

&H ZZ H WW

Design Goals Technology

• EM Calorimeters ( ) and Presampler ( )

• Hadronic Endcap ( )

• Forward Calorimeter ( )

2.30 8.10

GeVmm 8

GeVmrad 40

GeV27.0

%7.0GeV%10

EEEEE r

%10

GeV%100

jets%3GeV%50

EEE

%10GeV

%100jets

EE

2.35.1

3 5

LAr Calorimeter Technology Overview

Lead/Copper-Kapton/Liquid Argon Accordion Structure

Copper/Copper-Kapton/Liquid Argon Plate Structure

Tungsten/Copper/Liquid Argon Paraxial Rod Structure

LAr and Tile CalorimetersTile barrel Tile extended barrel

LAr forward calorimeter (FCAL)

LAr hadronic end-cap (HEC)

LAr EM end-cap (EMEC)

LAr EM barrel


Electromagnetic Barrel

0 1.4

Barrel Module Schematicwith presampler

• 64 gaps /module

• 2.1 mm gap

• 2x3100 mm long

Half Barrel Assembly

• 2x16 modules

• I.R/O.R 1470/2000 mm

• 22 - 33

• 3 longitudinal samples

•

• presampler

0X

0.025 0.025 1.8


Electromagnetic Endcap1.4 3.2

• 96 gaps /module outer wheel 32 gaps/module inner wheel

• 2.8 - 0.9 mm gap outer 3.1-1.8 mm inner

• 2x8 modules

• Diam. 4000 mm

• 22 - 37

• 3 longitudinal samples

•

• Front sampling of 6

for , - strips.

0X

0.025 0.025

0X2.5

2.5 0.1 0.1


Accordion Structure

Pb Absorber

• Honeycomb spacer &• Cu/Kapton electrode


Prototype of EM endcap

Detail of Kaptons


ATLAS FCAL

Pictures of assembly process

LAr Forward Calorimeters

• FCAL C assembly into tube – Fall 2003


ATLAS HEC Structure

Hadronic Endcap Calorimeter (HEC)

Composed of 2 wheels per endFront wheel: 67 t 25 mm Cu platesBack wheel: 90 t 50 mm Cu plates

Rear Wheel

Wheel Assembly

Front Wheel

Oct 2002

Electromagnetic Endcap

Hadronic Endcap

HEC – FCAL Assembly

Lar Endcap Installed in ATLAS

particle detectors for colliders calorimeters

Documents

triumf summer instituteb

triumf summer institutewhy

triumf summer institutecan

shower width

emmean hadronic

terms of molire radius

molire radius scales

brems photon of energynow