Nuclear & Particle Physics Flashcards
What is the the Thomsen Model?
It said electrons were spread out inside an atom
What was the Thomsen Model also known as?
The plum pudding model.
Why was the Thomsen also known as the plum pudding?
The atoms were s[heres of positive charge with tiny negative electrons stuck in them like fruit in a plum pudding.
What disproved the Thomsen Model?
Rutherford’s experiment.
What occurred in the Rutherford’s experiement?
-A stream of alpha particles from a radioactive source was fired at very thin gold foil.
-When alpha particles hits a fluorescent screen, a tiny flash of light occurs
-The flashes were counted, and counted the number of alpha particles at different angles
What would be observed if the Thomsen Model was right?
The flashes would be seen within a small angle of the beam
What was observed in Rutherford’s experiment?
-Most alpha particles went straight through the foil.
-Few were scattered at angles greater than 90, sending them back the way they came.
Rutherford’s model supported the idea of what?
It supported the idea of a small, positively charged nuclues
What conclusions did this experiment lead Rutherford to?
-Alpha particles went through the gold foil, so the atoms are mainly empty space
-Some were deflected at large angles, the centre of the atom must have a large positive charge to repel them.
-Very few were deflected at angles >90, so the diameter of the nucleus must be tiny compared to the atom.
-The ones that could only be deflected at angles >90 if they were scattered by something more massive than themselves, so most of the mass must be in the nucleus.
What are hadrons made of?
Quarks
What are the two types of hadrons?
-Baryons
-Mesons
+ their antiparticle counterpart
What particles are protons and neutrons are versions of?
Nucleons, they just have different electric charges.
What is a proton classified as?
Baryon
What is a neutron classified as?
Baryon
What is the proton’s unique characteristic compared to other baryons?
It is the only stable baryon and does not decay to other particles.
Give two antibaryons
-Antiprotons
-Antineutrons
What happens when antiparticles collide with each other?
They annihilated each other.
What quantum number is conserved in any interaction?
-Baryon number, the number of baryons in the particle.
-The baryon number must be the same on both sides of the interaction.
-If the numbers don’t match, the interaction can’t exist.
What is the baryon number of protons?
B= +1
What is the baryon number of a neutron?
B= +1
What is the baryon number of an antibaryon?
B= -1
How stable are mesons?
They are unstable.
What is the baryon number of a meson?
B=0
They’re not baryons
What are the lightest mesons?
Pions
Where would you get lots of pions?
In high-energy particle collisions.
Kaons compared to pions are…
…heavier and more unstable.
Where were pions and kaons discovered?
Cosmic rays
What type of particles are leptons?
They are fundamental particles, they are not made of anything smaller.
List 3 types of leptons
-Electrons
-Muons
-Taus
Muons and Taus compared to Electrons are…
… more unstable and heavier, and decay eventually to Electrons.
What does the electron, muon and tau come with?
Their own neutrino
How much mass and electric charge do neutrinos have
-Almost no mass
-Zero electric charge
Symbol, charge, lepton number for electrons?
e-
-1
Le=+1
Lμ=0
Lτ=0
Symbol, charge, lepton number for muons?
μ-
-1
Le=0
Lμ=+1
Lτ=0
Symbol, charge, lepton number for taus?
τ-
-1
Le=0
Lμ=0
Lτ=+1
Symbol, charge, lepton number for electron neutrino?
ve
0
Le=+1
Lμ=0
Lτ=0
Symbol, charge, lepton number for muon neutrino?
vμ
0
Le=0
Lμ=+1
Lτ=0
Symbol, charge, lepton number for tau neutrino?
vτ
0
Le=0
Lμ=0
Lτ=+1
What are photons?
When light behaves like particles and carries energy.
What do photons have?
No mass, charge, baryon and lepton numbers.
Symbol for photons?
γ
p̄
