Hadronic Calorimeters

HadronicCalorimeters

RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Hadronic CalorimetersRutgers Nuclear/Particle Physics Student Seminars

Raghav Kunnawalkam Elayavalli

Rutgers University, Relativistic Heavy Ion group with CMS, [email protected]

21st August 2013


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

1 Introduction

2 Hadronic Showers

3 LHC HCALs

4 Energy Resolution

5 References


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Introduction

Measures the energy (visible) of hadrons

Stops them (and particles that move through the ECAL)

indirect measurement of the presence of non-interacting,uncharged particles.

Sampling Calorimeters.


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Intro - contd.

First employed in the study of cosmic ray spectrum duringthe late 1950s.

E = ε∫n(x)dx - off by a factor of 2

Modern HCALs - Better understanding of Hadroniccascade

MC and Geant4 simulation studies of response


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Hadronic showers

E ≥ 1GeV

Interaction of a hadron with nucleus

elastic (p + N → p + N) : σel and inelastic(p + N → X ) : σel

hadronic interaction (collision) length:

λW =A

NA · ρ · σtot= 35A1/3(g/cm3)

interaction length - absorption N(x) = N0e−xλA

λA = ANA·ρ·σinel


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Hadronic showers - contd.

p+ nucleus → π+ + π− + π0 + · · ·+ nucleus

secondary particles undergo further inelastic collisions untilthey fall below pion production threshold

sequential decays π0 → γγ → electromagnetic showers

mean number of secondary particles ∝ lnE . typicalpT ≈ 350 MeV/c


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Longitudinal shower development

strong peak at nuclear absorption length λA

exponential decrease; need 11 λA to contain 99% of energy

Figure : Hadron shower development vs Photon shower


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Figure : Hadron Longitudinal shower depth in cm


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

CMS Slice

Figure : CMS detector


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Design Info

Used over a million World War II brass shell casementsfrom the Russian Navy

36 wedges - each weighs ≈ 40 tons

over 400 optical decoder units - made by US high schoolstudents.

Involved in assembling TestBeam’09 PMT readoutstructure.


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Towers

Figure : Design of a HCAL tower


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Readouts Structure

Figure : HCAL towers with their readouts in the CMS HF andschematic diagram of the readout structure


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

ATLAS HCAL

100% Analog vs CMS- 100% digital (video)


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Schematic of hits in a typical calorimeter

Figure : Cartoon showing the penetration and energy deposition foraverage energy entities in particle collisions.


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Energy Resolution of Hadron Caolrimeters

Intrinsic contributions - scale as 1/√E

Leakage fluctuations

Fluctuations of electromagnetic fraction

Nuclear excitations, fission, binding energy fluctuations · · ·Heavily ionizing particles

Fluctuations of invisible energySampling fluctuations


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Calorimeter requirements vs Reality

Signal ≈ Energy (linearity) - Nor completely linear

Gaussian distributed - Not completely gaussian

Resolution deviates from 1/√E dependence

Not independent of particle type - e/π or e/h ratio.


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

e/π issue

Figure : Ratio of the Electromagnetic and hadronic energy depositionfor different calorimeter materials


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

Compensation - Fixing

Software compensation:

Segmentation of calorimeter into cells/layers

Identification of cells/layers with particularly large energy(due to π0)

Give small weight to layers with larger energy density

Hardware compensation:

Varying absorber/active material thickness

Increase hadronic response via fission and spallation ofuranium

Increase neutron detection efficiency in active material[high proton content]


RaghavKunnawalkam

Elayavalli

Outline

Introduction

HadronicShowers

LHC HCALs

EnergyResolution

References

References

http://cms.web.cern.ch/news/hadron-calorimeter

http://cds.cern.ch/collection/Photos

The CMS hadron Calorimeter project : Technical DesignReport

http://www.physi.uni-heidelberg.de/ fschney/detektoren/Detektoren.IX.pdf

Calorimetry for Particle Physics, Christian W. Fabjan andFabiola Gianotti. CERN-EP/2003-075.

Hadronic Calorimeters

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