1. Learning Objectives Calorimetry and Showers
Understand the basic operation of a calorimeter
(Measure the energy of a particle, and in the process,
destroy it)
Understand the difference between an electromagnetic
shower and a hadronic shower
Understand the similarity between measuring a
particle’s energy with a calorimeter and with a
ground-based array of detectors (for cosmic ray
air showers)

2. Calorimetery and Showers
Outline
Introduction

3. Hadronic showers p+, p- p0 Calorimetry and Showers
In a hadronic shower, most of the scondaries are pions
Pions come in three charge states:
p+, p p0
They go on to either
Create another hadronic shower
Decay to a muon and two neutrinos
They decay immediately to two
photons (gg), which then create
electromagnetic showers
Particle masses (in energy units):
Electron MeV Fundamental particle
Muon 106 MeV Fundamental particle
Pion 140 MeV Two quarks
Proton 938 MeV Three quarks
p0 lifetime = 8.4  seconds
p+, p- lifetime = 2.6  10-8 seconds
Muon lifetime = 2.2  10-6 seconds

4. The longitudinal (depth) development of an electromagnetic shower
Calorimetry and Showers
The longitudinal (depth) development of an
electromagnetic shower
Pair production e+ g e- e- e-
Bremsstrahlung
Radiation length
Number of particles
…….

5. Examples of Calorimeter Read-out Schemes
Calorimetry and Showers
Examples of Calorimeter Read-out Schemes
Lead-scintillator
sandwich
Lead-liquid argon
sandwich
Lead-scintillator
sandwich with
wavelength-shifting
bars on side of module
Sandwich of lead and
multi-wire proportional
chambers

6. Measured energy distributions for 4 different
Calorimetry and Showers
Measured energy distributions for 4 different
incident electron energies
Width of
distribution
Average measured
energy
Above distributions come from measuring many, many
particles incident on the calorimeter
Note the spread in measured energies due to
statistical fluctuations in shower development

7. Calorimetry and Showers

8. Hadronic showers are deeper and wider than electromagnetic showers
Calorimetry and Showers
Depth development of a hadronic shower
Interaction length
Hadronic showers are deeper and wider than
electromagnetic showers

9. Calorimetry and Showers
Depth Development of Electromagnetic Showers
High energy
electrons
Low energy
electrons
Increasing depth in radiator material measured
in radiation lengths
Higher energy particles push “shower maxium”
deeper into material
Depth of shower maximum  ln (Energy electron,photon)

10. Calorimetry and Showers