Particle Physics Flashcards
To revise particle physics
1
Q
Describe the nuclear model of the atom
A
A positive nucleus containing protons and neutrons with electrons found in shells orbiting the nucleus
2
Q
State the relative charge of all sub atomic particles
A
Proton +1
Neutron 0
Electron -1
3
Q
State the relative masses of all sub atomic particles
A
Proton 1
Neutron 1
Electron almost 0 (1/1840)
4
Q
How can you calculate the specific charge? Giving all units
A
Specific charge (C/kg) = charge (C) / mass (kg)
5
Q
Charge/mass =
A
Specific charge
6
Q
Define atomic (proton number)
A
The number of protons in a nucleus = the number of electrons for an uncharged atom
7
Q
Define nucleon number
A
The number of nucleons (protons + neutrons)
8
Q
An element with the same number of protons but a different number of neutrons is called?
A
An isotope
9
Q
Define an isotope
A
An isotope is the same element with the same number of protons but different number of neutrons
10
Q
Why is the strong nuclear force important?
A
It keeps nucleus stable
11
Q
Sketch a graph of force against seperation for the strong nucear force.
A
Must be attractive and repulsive at different distance.
12
Q
When is the strong nuclear force attractive?
A
Between 0.5 and 3 fm
13
Q
When is the strong nuclear force repulsive
A
A distances closer than 0.5 fm
14
Q
Describe some properties of the strong nuclear force
A
- Very strong - overcomes repulsion between positive protons
- Very short range - only acts between adjacent nucleons
- Acts on any nucleon (proton or neutron) and is independent of charge
- Can be attractive or repulsive
15
Q
How does the strong nuclear force cause particles to be in equilibrium?
A
Increase in nucleon separation leads to an attractive force. Decrease in nucleon separation leads to a repulsive force In both situations, force will return nucleons back to equilibrium position.
16
Q
What are the three types of radioactive decay?
A
- Alpha
- Beta
- Gamma
17
Q
Describe an alpha particle
A
2 protons and 2 neutrons or a Helium nucleus
18
Q
State the ionizing ability of an alpha particle
A
Highly
19
Q
State the relative mass and charge of an alpha particle.
A
Mass = 4
Charge = +2
20
Q
State what can stop an alpha particle
A
10 cm air, skin or paper
21
Q
Describe a beta particle
A
fast moving electron ejected from the nucleus
22
Q
State the relative mass and charge of a beta particle?
A
Mass almost 0
Charge = -1
23
Q
State the ionizing ability of a beta particle?
A
Moderatly ionizing
24
Q
State what can be used to stop a beta particle?
A
A feww mm’s of aluminium
25
Describe a gamma wave
1. Electromagnetic wave that moves at the speed of light through a vacuum
2. Relative mass of 0
3. Relative charge of 0
4. very weakly ionising
5. Reduced by cm's lead or m's of concrete
26
State the relative mass and charge of a gamma wave.
Mass = 0
Charge = 0
27
State the ionizing ability of a gamma wave
Very weakly ionizing
28
State how gamma waves can be reduced
A few cm's of lead
29
Describe the changes that take place in beta decay
A neutron decays into a proton creating the beta particle and an electron antineutrino.
For a neutron to decay into a proton a down quark decays into a up quark
30
Describe the evidence that neutrinos exist
1. Experimental data shows that as a beta particle is emitted in beta decay it will have a range of energies from nearly zero up to a maximum.
2. All decays must have the same energy (conservation of energy)
3. The total energy and momentum of the beta particle and recoiling nucleus was not constant.
4. Energy has to be conserved Wolfgang pauli (1930) predicted a particle that could carry away the extra energy/momentum so they would be conserved. This particle was discovered and named the antineutrino
31
Describe the changes that take place in positron emission
A proton decays into a neutron creating the positron and an electron neutrino.
For a proton to decay into a neutron a up quark decays into a down quark.
32
Why does an antineutrino need to be released during beta decay
To conserve, energy, momentum and lepton number
33
Define a fundamental particle
Fundamental particles cannot be divided into other particles. They have no internal structure.
34
Give some examples of fundamental particles
Electron, neutrino, all quarks
35
What are the 6 types of quark
1. Up
2. down
3. top
4. bottom
5. strange
6. charm
36
What is the quark structure of a proton?
u u d
37
What is the quark structure of a neutron?
u d d
38
What is an antiparticle
particles with the same mass but opposite charge
39
State the name of the anti electron
Positron
40
Define a hadron
Hadrons are any particle made up of quarks.
Hadrons are not fundamental.
Hadrons can be either Baryons or mesons.
41
What force are hadrons subject to?
Strong nuclear force
42
Define a baryon
Baryons are made up of three quarks and have a baryon number of 1.
43
State some common baryons
Protons and neutrons
44
Which is the most stable baryon?
Proton
45
Define a meson
Mesons are classified as hadrons as they are made of quarks. Mesons contain a quark and an antiquark have a baryon number of 0
46
Name some typical mesons
Pions and Kaons
47
A particle made up of 3 quarks is called?
A baryon
48
A particle is that is made up of a quark and anti quark is called?
Meson
49
Name some leptons
Electrons, neutrinos, Tau, muon
50
State the mass and charge of a neutrino
mass = 0
charge = 0
51
What force controls leptons?
Leptons are subject to the weak nuclear force
52
What type of particle is a muon?
A lepton
53
In a nuclear event what must be conserved?
1. Charge
2. Baryon number
3. Lepton number
4. Energy
5. Momentum
54
What force of nature creates strange particles?
Strange particles are made through the strong interaction
55
What force allows strange particles to decay?
Strange particles decay through the weak interaction (e.g. Kaons)
56
Why must strange particles be created in pairs?
To conserve strangness
57
When must strangeness be conserved?
When strange particles are made in pairs. Strangeness is conserved with the strong interaction (only the weak interaction can change the type of quark, so there must be the same number of strange particles before and after)
58
When can strangeness change?
Strangeness can change by +1, 0 or -1 in the weak interaction when a strange particles decay
59
Define annihilation
If a particle and anti-particle meet they will annihilate each other and their entire mass is converted into energy into the form of **_two_** identical gamma photons (e.g PET scanners)
60
Why are 2 identical gamma photons produced in annihilation?
To conserve energy and momentum
61
How many gamma photons are produced in annihilation?
2
62
During annihilation what is the minimum energy of one the gamma photons equal to?
The rest mass of one of the original particles
Minimum energy of each photon = Eo
63
When a particle and antiparticle meet and the mass is converted into energy in the form of 2 gamma photons this is called?
Annihilation
64
Define pair production
In pair production a single photon vanishes and its energy is converted into mass in the form of a particle and its anti-particle.
65
What is the condition required for pair production?
This can only happen if the energy of the photon is enough to produce the (rest) mass of the particle and anti particle.
Min energy of photon = 2Eo
This normally happens near a nucleus to conserve momentum.
66
In pair production what happens if the initial photon has an energy greater than the rest mass of the particels and anti particle?
The particle and anti particle take the extra energy away as kinetic energy
67
What is the minimum energy for pair production?
Rest energy of particle + rest energy of antiparticle
68
What group of particles are made of quarks and are subject to the strong interaction?
Hadrons
69
What is quark confinement?
The energy required to produce a separation of two quarks far exceeds the pair production energy of a quark-antiquark pair, so instead of pulling out an isolated quark, you produce mesons as the produced quark-antiquark pairs combine.
70
Define an exchange particle
Exchange particles are how forces act between two particles.
They are virtual particles and only exist for a very short amount of time.
They can transfer energy, charge force and momentum
71
For the strong nuclear force state:
the particles affected
the name of the exchange particle
its range
Nucleons (all hadrons)
Gluons and Pions
Range up to 3 fm
72
For the electromagnetic force state:
the particles affected
the name of the exchange particle
Range
Charged particles
Virtual photons
infinite range
73
For the weak nuclear force state:
the particles affected
the name of the exchange particle
Range
Responsible for beta decay and changing quarks e.g u to d
W+, W- bosons
10-18 m
74
For the gravitational force state:
the particles affected
the name of the exchange particle
Range
all particles with mass
Gravitron
Infinite
75
What are the rules for drawing particle interaction diagrams
Rules for drawing particle interaction diagrams:
1. Exchange particles are represented by wiggly lines
2. Other particles are represented by straight lines
3. Incoming particles start at the bottom of the diagram and move upwards
4. Baryons stay on one side of the diagram and leptons on the other
5. The W boson carries charge from one side to the other (make sure charges balance)
6. A W- particle going to the left has the same effect as a W+ moving to the right
76
What is electron capture?
Electron capture is a process in which the proton-rich nucleus absorbs an electron. This process thereby changes a nuclear proton to a neutron and simultaneously causes the emission of an electron neutrino
77
What is an electron-proton collision?
An electron collides at high speed with a proton. The proton decays into a neutron and an electron neutrino.
78
What are the similarities and differences between electron capture and electron-proton collisions?
Similarities - both change a nuclear proton to a neutron and simultaneously causes the emission of an electron neutrino
Differences - In electron-proton collision the electron is the particle thats acting because its being fired at a proton so the W boson comes from the elctron. It must be the W- (moving to the left) to conserve charge. With electron capture the exchange particel is the W+(moving to the right)
79
Sketch and label a Feyman diagram for electron repulsion.
See diagram
80
Sketch and label a Feyman diagram for beta decay (in terms of protons and neutrons)
See diagram
81
Sketch and label a Feyman diagram for beta decay (in terms of quarks)
See diagram
82
Sketch and label a Feyman diagram for positron emmision (in terms of protons and neutrons)
see diagram
83
Sketch and label a Feyman diagram for electron capture
see diagram
84
Sketch and label a Feyman diagram for electron - proton collision
see diagram
85
Sketch and label a feyman diagram for a neutrino and neutron interaction where a beta particle and proton are created
See diagram
86
Sketch and label a feyman diagram for a antineutrino and proton interaction where a positron and neutron are created
see diagram
87
Under certain conditions a photon may be converted into a particle and it's corresponding antiparticle. Name this process
Pair production
88
What type of mesons are strange?
Kaons
89
What type of mesons are not strange?
Pions
90
State the quark structure of an antibaryon
3 antiquarks
91
Give one property of an antiparticle that is the same for its corresponding particle
Rest energy or Rest mass
92
Give one property of an antiparticle that is different to its corresponding particle
One of: charge, quark composition, baryon number, lepton number, strangeness
93
What is the baryon number of a Kaon or a Pion
0
94
What fundamental forces can an electron experience?
Weak, electromagnetic, gravitational (although negligible)
95
What fundamental forces can a proton experience?
Weak, strong, electromagnetic, gravitational (negligible)
96
What fundamental forces can a neutron experience?
Strong, weak, gravitational (negligible)
97
What force of nature is present when there is a virtual photon?
Electromagnetism
98
What force of nature is present when there is a gluon or pion?
Strong
99
What force of nature is present when there is a gravitron?
Gravity
100
What force of nature is present when there is a boson?
Weak interaction
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