Particles Flashcards
Which part of the atom has the largest specific charge and why?
The electron
(It has the same magnitude of charge as the proton but a much smaller mass)
Why do the proton, neutron and electron deflect differently in a magnetic field?
Neutron → 0 specific charge so zero deflection
Electron → Greatest specific charge so greatest deflection
Proton → Smaller deflection in opposite direction as specific charge smaller and opposite
How do you calculate the specific charge of a nucleus?
Divide the total charge of the protons by the total mass of nucleus
(Protons + Neutrons)
How do you calculate the specific charge of an ion?
Charge of the ion (Protons - Electrons) divided by total mass of ion
What is an isotope?
An atom with the
- same number of protons
- Different number of neutrons
When will an isotope undergo radioactive decay?
If the nucleus has:
- too many or too few protons
- Too many nucleons
- Too much vibrational energy
What happens in alpha (α) decay?
A nucleus ejects a helium nucleus (2 protons and 2 neutrons)
Decreasing its nucleon number by 4
And its proton number by 2
What happens in Beta Minus (β-) Decay?
A neutron turns into a proton
Ejecting a fast moving electron (β-) and an anti-electron neutrino
What happens in Beta Plus (β+) Decay?
A proton turns into a neutron
Ejecting a fast moving positron (β+) and an electron neutrino
What is wrong about this Beta Decay equation?
The nucleon number must not change
Why do the α, β-, β+ and γ deflect differently in a magnetic field?
α and β+ → Deflect in same direction but β+ larger (greater specific charge)
β- → Equal and opposite deflection to β+ (Equal and opposite specific charge)
γ → No deflection (no specific charge)
What is an antiparticle?
A particle with the:
- Same mass
- But equal and opposite charge
What happens during Annihilation?
A particle collides and annihilates with its correspond antiparticle
And their mass energy (E=mc2) is converted to radiation energy
Producing at least 2 gamma photons
Why do at least 2 photons need to be created during annihilation?
To conserve momentum
Before annihilation ptotal = 0
AFter annihilation ptotal = 0 (can’t be achieved with one photon)
What happens during pair production?
A gamma photon (with energy ≥ 2 × mass energy)
spontaneously creates a particle, anti-particle pair
What condition must pair production meet?
The energy of the gamma photon ≥ Mass energy of the particle anti-particle pair
(Any excess energy is used a kinetic energy for the particles produced)
How was the anti-electron neutrino discovered?
During Beta decay the emitted β- had less energy than expected so another particle carried the rest of the energy
What are the four fundamental forces and their approximate ranges?
- Strong
- Weak
- Electromagnetic
- Gravitational
What does the strong force do?
What is the exchange particle of the strong force?
Holds nucleons together in the nucleus
- By opposing the electromagnetic repulsion of the protons
- By attracting nucleons at small distances but repelling the, at very small distances
Gluons (between quarks), or pions (between hadrons)
Describe the nature of the strong force
Very repulsive over short distance (0-0.5fm)
Attractive over larger distances (0.5fm < d < 3fm)
Negligible beyond 3fm
What does the electromagnetic force act between and what is its exchange particle?
Acts between all particles with charge
Exchange particle is the photon
What does the gravitational force act between?
Particles or objects with mass
The exchange particle is the graviton
What particles does the weak force act on and what does it do?
Acts in any interaction leptons and hadrons (lepton-lepton or lepton-hadron) causes the decay of hadrons (by changing quark structure)
The exchange particles for the weak force are w+, w- & z bosons dependent on conservation of key values (QBLS) as z bosons have no charge whereas w bosons do
What are fundamental particles that make up the standard model? (that you need to know)
NOTE: Each of the leptons and and quarks has an corresponding anti-lepton and anti-quark
What is the quark structure of a proton?
Up, Up, Down
What is the quark structure of a neutron?
Up, down, down
How is a muon different from an electron?
Both are leptons, muon is much heavier than the electron, produced in cosmic ray showers
What are hadrons?
Particles that are made up of quarks
How are baryons and mesons different?
Both are hadrons (made up of quarks)
But Baryons are made up of 3 quarks
And Mesons are made up of 1 quark 1 anti-quark
What are the similarities and differences between W bosons and photons?
Both are exchange particles
But W bosons mediate the weak force, Photons mediate electromagnetic
W bosons carry charge of +1 or -1, Photons have no charge
W bosons have mass, Photons are massless
What are the similarities and differences between gluons and pions?
Both mediate the strong force
But gluons act between quarks, Pions act between hadrons (to keep the nucleus together)
Gluons have no mass, Pions have mass
What does the Higgs Boson do?
It creates the Higgs field
Which gives mass to particles
What quantities are always conserved in every interaction?
- Total momentum
- Total energy
- Charge
- Baryon
- Lepton number
NOTE 1: Kinetic energy is conserved in elastic collisions
NOTE 2: Strangeness is conserved in all interactions apart from weak
What must you know about k-mesons? (kaons)
They are made of 1 quark and 1 anti-quark (mesons)
They have non-zero strangeness
Produced by strong interactions, Decay (into pions) by weak interactions
What must you know about π-mesons? (pions)
They are made up of 1 quark and 1 anti-quark (mesons)
They have strangeness = 0
What is the most stable lepton and what is the most stable hadron?
(That other isolated particle will eventually decay into)
The electron and the proton
Why can’t this muon decay happen like this?
(What’s the mistake with the logic in the table?)
When electron and muon type particles are involved each lepton number must be considered separately
What is the formula for a muon decaying into an electron?
What is the feynman diagram for an electron-electron collision?
What is the feynman diagram for β- Decay?
What is the feynman diagram for β+ Decay?
What is the quark feynman diagram for β- Decay?
What is the quark feynman diagram for β+ Decay?
Identify the unknown particles in this feynman diagram for electron capture
Identify the unknown particle in this feynman diagram for the electron proton collision
Identify the unknown quark in the feynman diagram for electron capture
Identify the unknown exchange particle in the quark feynman diagram of electron proton collision
Which particles have a baryon number = +1?
Which have a B = -1?
Which have a B = 0
Baryons = +1
Anti-Baryons = -1
All other particles (including mesons) = 0
Which particles have a Lepton number = +1?
Which have a L = -1?
Which have a L = 0
Leptons = +1
Anti-Leptons = -1
All other particles = 0
What is the muon lepton number of an electron?
0! Only muons and muon neutrinos have Lmuon = +1
What is the electron lepton number of a muon?
0! Only electrons and electron neutrinos have Lelectron = +1
What is the formula for electron capture?
AZX + 0-1e-1 → A Z-1Y+ ve
proton turns into a neutron
You do not need to know this
What is the formula for neutron emission?
AZX → A-1ZY + 10n
You do not need to know this
What is the formula for proton emission?
AZX → A-1Z-1Y+ 11P
You do not need to know this
Why was the Antiproton not discovered until 1955?
It was only then that large enough particle accelerators were built in order to form large enough particles
Why can’t particles such as muons or leptons decay into baryons?
Particles can’t decay into bigger particles than themselves
Why are quarks only found in baryons and mesons?
Quarks cannot exist on their own
Why did it take so long for the Higgs boson to be discovered?
Was not discovered until 2012 as there was not a particle accelerator big enough to form the particle until CERN
Which exchange particles have mass?
W+, W-, Z0
Which exchange particles have charge?
W+, W-
What is the case at junctions of Feynman diagrams?
All conservation laws apply
How are particles and exchange particles represented on Feynman diagrams?
Exchange particles - wiggly lines
Particles - straight lines
What is on the y-axis for feynman diagrams?
Time
Which other quark can strange quarks decay into?
Up quarks
Which quark is the heaviest
Strange quark
