Basic Concepts of Calorimetry Yasmine Israeli Yasmine Israeli - - PowerPoint PPT Presentation

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Basic Concepts of Calorimetry Yasmine Israeli Yasmine Israeli IMPRS Colloquium, December 2016 1 Outline What is a calorimeter Different particle showers Calorimeter types Problem in detecting an hadron Why hadronic and EM

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Basic Concepts of Calorimetry

Yasmine Israeli

Yasmine Israeli IMPRS Colloquium, December 2016 1

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Outline

  • What is a calorimeter
  • Different particle showers
  • Calorimeter types
  • Problem in detecting an hadron
  • Why hadronic and EM calorimeters
  • Energy reconstruction
  • Energy resolution
  • Detection in the calorimetry system

Yasmine Israeli IMPRS Colloquium, December 2016 2

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What is a Calorimeter?

Calorimeter measures the energy of an incoming particle.

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s (shower’s) energy into something detectable

(like photons, charge).

Yasmine Israeli IMPRS Colloquium, December 2016 3

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What is a Calorimeter?

Calorimeter measures the energy of an incoming particle.

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s (shower’s) energy into something detectable

(like photons, charge).

  • Detects more stable particles e±, γ, π±, π0, K ±, K 0, p±, n

(µ± don’t induce showers) Yasmine Israeli IMPRS Colloquium, December 2016 3

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What is a Calorimeter?

Calorimeter measures the energy of an incoming particle.

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s (shower’s) energy into something detectable

(like photons, charge).

  • Detects more stable particles e±, γ, π±, π0, K ±, K 0, p±, n

(µ± don’t induce showers)

”Ideal” calorimeter: Calorimeter signal ∝ deposited energy ∝ energy of primary particle

Yasmine Israeli IMPRS Colloquium, December 2016 3

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Particle Showers

  • a high-energy particle interacting with dense matter.
  • secondary particles are produced
  • each secondary particle interacts with the same dense matter and

produces more particles

  • This process continues → the particle number is growing as long as the

energy of the ”secondaries” is sufficient to create new particles

Yasmine Israeli IMPRS Colloquium, December 2016 4

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Particle Showers

Shower length scales:

  • EM Shower: Radiation length X0
  • Had. Shower: Interaction length λInt

Simplified Model:

  • 1 Step = X0 ⇒ 2 new particles
  • t Steps = t ⋅ X0 ⇒ 2t particles,with E = E02−t (E0 energy of initial particle)
  • tmax steps = shower maximum, E = ǫc

tmax = log2(E0 ǫc ) ⇒logarithmic increase of shower depth with E0

Yasmine Israeli IMPRS Colloquium, December 2016 4

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EM Showers

Origin: energtic e−,e+ or γ interacts with dense matter → e−,e+,γ

  • electron-positron pairs
  • photo-electric effect
  • Bremsstrahlung
  • ionization

Yasmine Israeli IMPRS Colloquium, December 2016 5

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Hadronic Showers

Origin: π±, K ±, K 0, p± or n entering dense matter → strong interaction!

  • spallation
  • excitation of nuclei
  • production of hadrons and mesons
  • nuclear fission
  • EM sub-shower: natural measons (π0, η) →photons

⋆pair production ⋆photo-electric effect ⋆Bremsstrahlung ⋆ionization Yasmine Israeli IMPRS Colloquium, December 2016 6

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Calorimeter Types:

Calorimeter { Absorbs the particle by generating shower↔ Absorber Converts particle′s energy into something detectable↔ Detector

Yasmine Israeli IMPRS Colloquium, December 2016 7

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Calorimeter Types:

Calorimeter { Absorbs the particle by generating shower↔ Absorber Converts particle′s energy into something detectable↔ Detector Homogenous Calorimeter

  • Absorber+detector in one medium
  • Measures the complete energy deposit

Sampling Calorimeter

  • Absorber and detector are separated
  • Showers develop in passive layers
  • Particles are detected in active layers

Yasmine Israeli IMPRS Colloquium, December 2016 7

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Homogeneous Calorimeter

Absorber+detector in one medium

  • Dense scintillating crystals
  • lead loaded glass (Cerenkov light)
  • Noble gas liquids

Read-out ⋆Mostly based on light detection:

  • Photomultiplier
  • Avalanche Photo-Diodes
  • Silicon-Photo-multipliers
  • Cherenkov detectors

⋆Always at the end

Yasmine Israeli IMPRS Colloquium, December 2016 8

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Calorimeter Types: Sampling Calorimeter

Absorber and detector are separated ⇒flexible and compact design Passive Layers:

  • Generate the shower
  • High density, high atomic number

▸ iron, lead, uranium

Active layers:

  • Record the particle within the shower
  • Different technologies can be applied

▸ Plastic scintillators+ photo-detectors ▸ Silicon detectors ▸ Noble liquid ionization chambers ▸ Gas detectors

Yasmine Israeli IMPRS Colloquium, December 2016 9

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Homogenous vs Sampling

Homogenous Calorimeters:

  • Good energy resolution for EM showers
  • Very non-linear for hadrons
  • Limited granularity
  • Crystals are expensive
  • no direct information on shower development

Sampling Calorimeters:

  • Compact
  • Flexible design
  • Can be cheap
  • Energy resolution is limited by sampling fluctuations

↪ The fractions of how much is energy is deposited in the absorber and in the detector varies from event to event

Yasmine Israeli IMPRS Colloquium, December 2016 10

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Problem: Detecting an Hadron

Calorimeter:

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s shower’s energy into something detectable
  • Our detectors detect: Charge or Photons

Yasmine Israeli IMPRS Colloquium, December 2016 11

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Problem: Detecting an Hadron

Calorimeter:

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s shower’s energy into something detectable
  • Our detectors detect: Charge or Photons

In EM shower: e−, e+ or γ produces more e−, e+, γ

  • Yasmine Israeli

IMPRS Colloquium, December 2016 11

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Problem: Detecting an Hadron

Calorimeter:

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s shower’s energy into something detectable
  • Our detectors detect: Charge or Photons

In EM shower: e−, e+ or γ produces more e−, e+, γ

  • In hadronic shower: invisible energy!!
  • nuclear binding energy
  • slow neutrons
  • neutrinos
  • The fraction of invisible energy varies
  • The fraction of the electromagnetic sub-shower varies
  • Yasmine Israeli

IMPRS Colloquium, December 2016 11

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Problem: Detecting an Hadron

Calorimeter:

  • Stops (absorbs) the particle by generating showers.
  • Converts particle’s shower’s energy into something detectable
  • Our detectors detect: Charge or Photons

In EM shower: e−, e+ or γ produces more e−, e+, γ

  • In hadronic shower: invisible energy!!
  • nuclear binding energy
  • slow neutrons
  • neutrinos
  • The fraction of invisible energy varies
  • The fraction of the electromagnetic sub-shower varies
  • e detection

π detection > 1

Yasmine Israeli IMPRS Colloquium, December 2016 11

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  • Had. and EM Calorimeters?!

EM Showers:

  • e±, γ production
  • EM shower size ∝ to radiation length X0

Hadronic Showers:

  • Hadrons, mesons, baryons production.
  • EM sub-shower:e±, γ production
  • Had. shower size ∝interaction length λInt

Yasmine Israeli IMPRS Colloquium, December 2016 12

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  • Had. and EM Calorimeters?!

EM Showers:

  • e±, γ production
  • EM shower size ∝ to radiation length X0

Hadronic Showers:

  • Hadrons, mesons, baryons production.
  • EM sub-shower:e±, γ production
  • Had. shower size ∝interaction length λInt

X0 < λInt ⇒ EM showers are more compact!

Yasmine Israeli IMPRS Colloquium, December 2016 12

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  • Had. and EM Calorimeters?!

EM Showers:

  • e±, γ production
  • EM shower size ∝ to radiation length X0

Hadronic Showers:

  • Hadrons, mesons, baryons production.
  • EM sub-shower:e±, γ production
  • Had. shower size ∝interaction length λInt

X0 < λInt ⇒ EM showers are more compact! EM shower* usually:

  • Starts before Had. shower.
  • Every ”generation” in the shower happens in a smaller scale.
  • The shower ends before the Had. shower

* also the EM sub-shower in the Had. shower Yasmine Israeli IMPRS Colloquium, December 2016 12

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  • Had. and EM Calorimeters?!

A small EM calorimeter before Had. calorimeter

  • Using two different technologies

↪can use homogeneous calorimeter for Ecal (EM calorimeter).

  • Optimizing Ecal for EM showers (including the EM sub-shower)
  • Optimizing Hcal (hadronic calorimeter) for Had. showers
  • Different granularity (cell size in the detector) is needed
  • Cheaper
  • Improving the energy resolution

Yasmine Israeli IMPRS Colloquium, December 2016 13

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Standard Energy Reconstruction:

For each event:

  • Collect all the signal’s energy from Ecal : E Ecal

total = ECal

∑

All signals

Esignal

  • Collect all the signal’s energy from Hcal : E Hcal

total = HCal

∑

All signals

Esignal

  • Add together, including calibration factors for each detector:

E event

reco

= E Ecal

total ⋅ ωE + E Hcal total ⋅ ωH

All events:

  • Fill a histogram with ”enough” events
  • Determine what is Ereco and ∆Ereco/Ereco

Yasmine Israeli IMPRS Colloquium, December 2016 14

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Energy Reconstruction in CALICE:

SiW ECAL

  • Silicon sensors
  • Absorber : tungsten

AHCAL+TCMT

  • SiPM
  • Absorber : steel
  • Gaussian fit

⇒ µ, σ

  • Energy resolution: σreco

Ereco

E [GeV] 10 20 30 40 50 60 500 1000 1500 2000 2500

/E=0.0977 σ =35.3704, µ Standard Reco.,

[GeV]

rec

E 10 20 30 40 50 60 70 80 CERN TB

  • π

CALICE Prototype, Standard Reco. [GeV]

beam

E 10 20 30 40 50 60 70 80

beam

)/E

beam
  • E
rec

(E 0.04 − 0.02 − 0.02 0.04

Yasmine Israeli IMPRS Colloquium, December 2016 15

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Energy Resolution

∆E0 E0 = σ(E0) E0 = a √E0 ⊕ b E0 ⊕ c

Stochastic term: Fluctuation in the number of measured particles (a simple statistical error) Noise term: Readout electronic noise, pile-up fluctuations Constant term: ⋆ Non-uniform detector response ⋆ Channel to channel inter-calibration errors ⋆ Fluctuations in longitudinal energy containment ⋆ Energy lost in dead material, before or in detector

[GeV]

beam

E 10 20 30 40 50 60 70 80

rec

/E

rec

σ 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Standard Reco. c / E ⊕ b ⊕ E Fit: a /

  • St. Reco. a=53.39% b=3.37% c=0.18

Yasmine Israeli IMPRS Colloquium, December 2016 16

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Detection in the Calorimetry System

e+e− → Zh → µ+µ−h

Yasmine Israeli IMPRS Colloquium, December 2016 17

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Detection in the Calorimetry System

e+e− → Zh → µ+µ−h

Yasmine Israeli IMPRS Colloquium, December 2016 17

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Detection in the Calorimetry System

e+e− → Zh → µ+µ−h

Yasmine Israeli IMPRS Colloquium, December 2016 17

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Detection in the Calorimetry System

e+e− → Zh → µ+µ−h

Yasmine Israeli IMPRS Colloquium, December 2016 17

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Summary

  • We can measure particle’s energy with calorimeters.
  • There are many different technologies in use.
  • The main challenge is detecting hadrons.
  • Good energy resolution is essential for valid reconstruction.
  • Calorimeter R&D is an active field.

Yasmine Israeli IMPRS Colloquium, December 2016 18

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Thank you for your attention!

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BACKUP

Yasmine Israeli IMPRS Colloquium, December 2016 20

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Local Software Compensation:

Problem in detection: e π > 1 ⇒ Lost energy in the hadron decay.

  • EM showers are denser than hadronic showers.

→ Classification of hits based on the energy density

  • χ2 minimization:

χ2 = ∑

events

( ∑

hits

Ehitωj − Ebeam)

2 j=Energy density index

Energy Density[MIP/cell] 5 10 15 20 25 30 35 40 45 50 0.05 MIP/cell) × hits/(events

  • 5

10

  • 4

10

  • 3

10

  • 2

10

  • 1

10 1 10

  • π

AHCal: Data 10

j density bin index

2 4 6 8 10

) [GeV/MIP] j,E ( ω

0.01 0.02 0.03 0.04 0.05

CALICE work in progress

AHCal weights: 80GeV 60GeV 50GeV 40GeV 20GeV 10GeV

Yasmine Israeli IMPRS Colloquium, December 2016 21