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A Level Physics > Particle Physics > Flashcards

Particle Physics Flashcards

Glover

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1
Q

strong force properties (5)

A
  • short-range attraction up to ~ 3 fm
  • very-short range repulsion closer than ~ 0.5 fm
  • Mediated by gluons/pions
  • Negligible beyond this range of 3 fm
  • Only affects hadrons
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2
Q

What does the strong nuclear force do?

A

Holds the nucleons together in the nucleus
Prevents the atom from collapsing at very short distances - short range

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3
Q

What is an excited electron?

A

When an electron temporarily occupies an energy state greater than its ground (normal/stable) state i.e. the electron has extra (kinetic) energy such as from absorbing a photon or it is collided into by an atom/particle

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4
Q

general symbol equation for beta minus decay

A

ᴬZX -> ᴬZ+1Y + ⁰-1β + ν̄e (greek letter nu - ν with fancy flicks on the top)

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5
Q

What is released in beta minus decay?

A

A proton, beta particle and antineutrino is released

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6
Q

Where does the beta particle released from beta minus decay come from?

A

The e- in this case is a fast moving electron emitted from within the nucleus through the decay of a neutron into a proton, and not an atomic electron that orbits around the nucleus.

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7
Q

What are the two purposes of an antineutrino in beta minus decay?

A

To carry away some energy and momentum.

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8
Q

Explain how the neutrino was hypothesised as a result of beta decay.

A
  • The energy of the other products was observed to be less than before the beta decay, as if energy was being lost.
  • Thus a particle must be emitted with a neutral charge and small mass for energy to be conserved.
  • This hypothesised particle was called the neutrino (now an antineutrino).
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9
Q

Where and when is gamma radiation emitted?

A

Only from the nucleus after beta or alpha emission.

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10
Q

Why is gamma radiation emitted?

A

To release energy, making the nucleus stable.

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11
Q

parent nucleus

A

the atomic nucleus that decays in radioactive decay to form smaller, lighter daughter nuclei

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12
Q

daughter nucleus

A

a new atomic nucleus formed after radioactive decay

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13
Q

State two ways that pair production of a positron and an electron differs from positron emission.

A

In pair production, no proton is involved and no neutrino is emitted.

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14
Q

positron emission

A

A fancy way of saying beta plus decay

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15
Q

Explain where pair production occurs.

A

Usually near a nucleus which recoils to conserve momentum.

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16
Q

specific charge formula

A

charge / mass

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17
Q

photon meaning

A

A particle representing the smallest quantum (packet) of EM radiation

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18
Q

What is E=hf used for?

A

the energy carried away by a photon

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19
Q

1MeV = ?

A

1.6 x 10-13V
(this stems from the [modulus] charge of an electron by definition of an eV)

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20
Q

What is a PET scanner and how does it work?

A

Positron Emission Tomography (something that produces a 3D image of the internal structures of a solid object)

A scanning technique that uses beta plus decay to stimulate annihilation. This produces gamma rays that can be detected to make cross-sectional and 3D images of tissues and organs

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21
Q

electron volt meaning

A

how much energy it takes to move an electron across a p.d. of 1 volt (found by inputting the value and charge of an electron into E=QV)

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22
Q

rest mass meaning and unit

A

When an object is stationary, all other energy can be ignored (assumed to be zero) so only the mass contributes to the object’s energy

Measured in kg

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23
Q

hadron

A

Particles made of quarks that can feel the strong nuclear force/strong interaction. The two types are baryons and mesons.

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24
Q

baryon
(+ how do they decay?)

A

A type of hadron made of three quarks. Except for protons, they are all unstable so decay (eventually into protons)

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25
Q

meson

A

A type of baryon with a quark and an antiquark

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26
Q

examples of baryons

A

e.g. neutrons and protons

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27
Q

examples of antibaryons

A

antiprotons and antineutrons

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28
Q

baryon number

A

The number of baryons. It is a quantum number that must be conserved i.e. particle interactions where the baryon number changes can’t happen.

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29
Q

What is the baryon number of an antineutron?

A

-1

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30
Q

What is the baryon number of an electron?

A

0

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31
Q

examples of mesons

A

e.g. pions and kaons

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32
Q

What is the antiparticle of π+?

A

π-

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33
Q

What is the antiparticle of π0?

A

π0 itself

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34
Q

pion role in physics

A

The exchange particle of the strong nuclear force.

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35
Q

What are pions made of?

A

A quark and an antiquark (it’s a meson)

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36
Q

What do kaons decay into?

A

Pions (e.g. pion+ and pion- particles)

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37
Q

How can you detect mesons?

A

High-energy (cosmic) rays from space often interact with molecules in the atmosphere to produce lots of high-enegy particles e.g. pions and kaons.

You can use a cloud chamber with two Geiger counters above each other to detect these particles and observe their tracks (when both detect radiation at the same time).

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38
Q

lepton

A

Very light fundamental particles that don’t interact with the strong nuclear force. They interact with the weak force (plus a bit of the gravitational force and the electromagnetic force if they’re charged)

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39
Q

A particle is made up of 3 quarks: dds.
A student says that the particle is a lepton. Is this true and explain why.

A

Not true as leptons aren’t made of quarks

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40
Q

lepton examples (give at least three)

A

e.g. electrons, muons, (electron & muon) neutrinos and their antiparticles

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41
Q

muon (+ what they can decay into)

A

Unstable, heavy electrons. They eventually decay into electrons

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42
Q

neutrino

A

Very small mass and no charge. They only interact in weak interactions

Italian for “little neutral one”

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43
Q

lepton number

A

The number of leptons. It is a quantum number that must be conserved i.e. particle interactions where the lepton number changes can’t happen.
There are two different lepton numbers; Le and Lμ

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44
Q

A neutron decays into a proton. Is the lepton number conserved in this interaction?

A

n -> p + ⁰-1β + ν̄e
neutron = lepton number 0
proton = lepton number 0
electron = lepton number 1
antineutrino = lepton number -1

lepton number of reactant = 0
lepton number of product = 1 - 1 = 0
so lepton number is conserved

45
Q

What is an antihadron made of?

A

Antiquarks

46
Q

Difference between the strong interaction and the weak interaction

A

Strong: attractive force between nucleons that holds the nucleus together

Weak: acts inside of individual nucleons that allows the decay of protons into neutrons and vice versa through beta decay

47
Q

When is strangeness conserved?

A

Conserved in the strong interaction but not the weak interaction

48
Q

How are strange particles created and how do they decay?

A

Created in the strong interaction but decay in the weak interaction

49
Q

If strangeness is conserved, how are strange particles created? Give an example

A

They are created in pairs e.g. K+ & K-

+1 - 1 = 0 strangeness

50
Q

charge of a strange quark

A

-1/3

51
Q

strangeness of a strange quark

A

-1

52
Q

baryon number of an up quark

A

1/3

53
Q

baryon number of a down quark

A

1/3

54
Q

baryon number of a strange quark

A

1/3

55
Q

Explain whether strangeness is a quantum number or not.

A

It reflects
the fact that strange particles are always created in pairs.

56
Q

What are pions made of?

A

A quark and an antiquark

57
Q

What does the weak interaction do?

A

Changes the type of quark
(e.g. neutron to proton in beta-minus decay)

58
Q

strangeness of a strange quark

A

-1 strangeness

59
Q

strangeness of an anti-strange quark

A

+1 strangeness

60
Q

K+ composition

A

strangeness = +1

u s-bar

61
Q

K0 composition

A

strangeness = +1

d s-bar

62
Q

anti K0 composition

A

strangeness = -1

s d-bar

63
Q

Pion + composition

A

u d-bar

64
Q

strangeness of a neutrally-charged meson

A

+1 or -1
It depends on whether it’s a
K0 quark (d s-bar) or the K0 antiquark (d-bar s)

65
Q

How is a muon related to an electron?

A

A muon is a particle like an electron with a greater mass.

66
Q

What is conserved in a particle interaction?

A
  • baryon number
  • lepton number
  • strangeness (strong interactions)
  • energy
  • momentum
67
Q

quark confinement

A

At the moment, quarks are called fundamental particles - you get pair production to form mesons.

You never find a quark alone

68
Q

What does the “weak” in weak interaction mean?

A

Low probability that it (decays) will happen.

69
Q

What is the strong force felt by?

A

Hadrons (incl. nucleons)

70
Q

What is the weak force felt by?

A

Any particles

71
Q

What is the weak interaction involved in?

A

Particle decays e.g. beta minus and plus decays

72
Q

How can you tell if a decay is caused by the strong interaction or the weak interaction?

A
  • Strong interaction only affects hadrons - if there’s a lepton, it must be the weak force.
  • The strong interaction can’t change quark flavour i.e. type (but it can annihilate/create pairs of the same quark flavour)
73
Q

Is the interaction below weak or strong? Is it possible?
K+ -> π+ + π0

A

Weak because it involves a change in quark flavour. It is possible (all conservation laws are followed, strangeness isn’t but that’s ok because it’s weak)

74
Q

exchange particles for the strong force

A

Pions between baryons e.g. in the nucleus for the strong nuclear force

Gluons between quarks (much smaller distances)

75
Q

exchange particle for electromagnetic interactions

A

virtual photon - fluctuations in the electromagnetic field which allow electrically charged particles to interact (by exchanging these virtual photons)

76
Q

exchange particles for the weak force

A

W+, W-, Z0 bosons

77
Q

exchange particle for the gravitational force

A

graviton - a massless particle that attracts masses together (although is very weak on its own)

78
Q

boson meaning

A

Particles that carry energy and so forces throughout the universe; exchange particles.

79
Q

gauge boson

A

Fundamental exchange particles for the four fundamental forces

80
Q

Compare the ranges of the four fundamental forces.

A

Longest to shortest:
Gravitations & electromagnetic - infinite range
Strong nuclear
Weak nuclear

81
Q

Feynman diagram for two positrons repelling each other

A

virtual proton in wavy line

82
Q

Feynman diagram for electron-proton collisions

A

W– boson goes from the electron to the
proton
neutron and electron neutrino are formed

83
Q

Feynman diagram for electron capture

A

W+ boson goes from the proton to the electron
neutron and electron neutrino are formed

84
Q

Feynman diagram for beta-minus decay

A

W- boson
neutron decays
proton, beta particle and electron antineutrino are formed

85
Q

Feynman diagram for beta-plus (anti-beta) decay

A

W+ boson
proton decays
neutron, positron and electron neutrino are formed

86
Q

purpose of the W bosons in a Feynman diagram

A

carry charge from one side of the diagram to the other

87
Q

A W– particle going to the left has the same effect as a ____ particle going to the ____.

A

W–, right

88
Q

How does a proton interact?

A

strong, weak and electromagnetic

89
Q

How does an electron interact?

A

weak and electromagnetic

90
Q

How does a neutron interact?

A

strong and weak

91
Q

How does a neutrino interact?

A

weak

92
Q

How does a muon interact?

A

weak and electromagnetic

93
Q

How do pions interact?

A

strong (and electromagnetic if charged)

94
Q

How do kaons interact?

A

strong (and electromagnetic if charged)

95
Q

What type of interaction acts when a muon decays?

A

weak

96
Q

What type of interaction acts when a pion decays?

A

strong

97
Q

What type of interaction acts when a kaon decays?

A

strong

98
Q

Strange particles always:
Are produced through the ____ interaction, decay through the ____ interaction
Are produced in __________ ___.

summary flashcard

A

strong, weak, quark-antiquark pairs

99
Q

strange particle half life

A

long - this is strange

100
Q

What particles are produced when a muon decays?

A

A muon neutrino, an electron, and an electron antineutrino

Muon neutrino - for muon lepton number conservation
Electron - for charge conservation
Electron neutrino - for electron lepton number conservation

101
Q

similarity & difference between muon & negative pion

A
  • both have a negative charge
  • pion experience the strong force whereas muons do not
102
Q

Kaons are mesons that can be produced by the strong interaction.
π- + p -> K0 + Λ0
Deduce the quark structure of the Λ0.

A

π- = d u-bar
p = uud
K0 = d s-bar

Λ0 must have a strangeness of -1 and a charge of 0
therefore quarks = u d s

103
Q

Explain why it is necessary for many teams of scientists and engineers to collaborate in order for advances in our understanding of particle physics to be made. [2]

A

Any two from:
* Many different skills are required
* Lots of teams need to collaborate to fund particle accelerators as they are expensive
* Results must be peer reviewed before they can be accepted

104
Q

Explain which fundamental interaction is responsible for electron capture.

A

Weak interaction/weak nuclear force because there’s a change in quark composition/flavour (u -> d)
OR because it involves hadrons and leptons

105
Q

A potassium isotope can decay by a decay process to form a calcium-40 nuclide.
Suggest how the emissions from a nucleus of decaying potassium can be used to confirm which decay process is occurring. [3]

A
  • beta (minus) emission
  • releases an electron
  • releases an antineutrino
  • no photon is released
  • details of how electron can be detected e.g. cloud chamber
106
Q

The antiproton produced interacts with a proton. State what is produced.

A

Two gamma ray photons

107
Q

Explain why a proton cannot be produced on its own.

A

A proton has a relative charge of +1 and a baryon number of 1, so charge and baryon number wouldn’t be conserved. This means a particle-antiparticle pair must always be produced.

108
Q

Higgs boson

A

A fundamental particle that is believed to be responsible for mass. It is one of countless Higgs bosons that make up the Higgs field, which particles interact with to give them their mass

109
Q

Name three particle interactions where a proton changes into a neutron.

A
  • Beta plus decay
  • Electron capture
  • Proton-electron collision

A Level Physics (4 decks)

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