particle detectors - rhigrhig.physics.wayne.edu/reu/new_talks/harr-particledetectors.pdfparticle...
TRANSCRIPT
Particle Detectors
How to See the Invisible
2
How are Subatomic Particles Seen?
3
How are Subatomic Particles Seen?
By their interactions with ordinary matter.
Ionization of atoms or lattice Interaction with nucleus
Pair production
Bremstrahlung
Transition radiation
Cherenkov radiationScintillation
Synchrotron radiation
4
Which Subatomic Particles are Seen?
Which particles live long enough to bevisible in a detector?
5
Which Subatomic Particles are Seen?
Which particles live long enough to bevisible in a detector?
Protons
electrons
photons
neutrons
6
Which Subatomic Particles are Seen?
Which particles live long enough to bevisible in a detector?
Protons
electrons
photonsAnti-protons
positrons
muons and anti-muons
charged pions
neutrons anti-neutrons
neutral kaonscharged kaons
A few special cases of strange baryons.
A General Purpose Detector
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Energy Loss
Muon momentum
1
10
100
Sto
ppin
g po
wer
[M
eV c
m2 /
g]
Lin
dhar
d-Sch
arff
Bethe-Bloch Radiative
Radiativeeffects
reach 1%
µ+ on Cu
Without !
Radiativelosses
"#0.001 0.01 0.1 1 10 100 1000 104 105 106
[MeV/c] [GeV/c]
1001010.1 100101 100101
[TeV/c]
Anderson-Ziegler
Nuclearlosses
Minimumionization
Eµc
µ$
Dependence on Material
1
2
3
4
5
6
8
10
1.0 10 100 1000 10 0000.1
Pion momentum (GeV/c)
Proton momentum (GeV/c)
1.0 10 100 10000.1
1.0 10 100 10000.1
1.0 10 100 1000 10 0000.1
!dE/d
x (M
eV g!1cm
2 )
"# = p/Mc
Muon momentum (GeV/c)
H2 liquid
He gas
CAl
FeSn
Pb
Energy loss depends on the type of material and particle.
Atoms with more higher Z have less energy loss per g/cm2
But their higher density (g/cm3) more than makes up for this.
Cerenkov Radiation
Emitted when a particle exceeds the speed of light in a medium
Like the shock wave from a supersonic plane
Cone angle is related to particle velocity
Scintillation
Many materials emit light when atoms or molecules are excited by a charged particle passing nearby
Emitted light is called scintillation
Scintillating medium usually transparent
Light (single or few photons) detected by a photomultiplier
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The Fundamental Particles
The particle physicist’s periodic table consists of:
3 generations of quarks3 generations of leptons4 force carriers
The quarks and leptons are fermions, the force carriers are bosons.
How Do We Study Particles?Experiment:
Collide ParticlesAt very high energies
and convert energy intomass (i.e. other particles)
Where Are Particle Colliders?
FermiLab (Batavia, IL) CERN (Geneva Switzerland)
Some Examples:proton and neutron composed of up (u) and down (d) quarksproton is only stable hadron (baryon or mesonanti-proton and anti-neutron composed of anti-up and anti-down quarkspions are mesons composed of u and d quarksheavier baryons and mesons exist containing s, c, and b quarks (all are unstable)top decays before it can form bound states (earlier cartoon)
What About the Higgs?