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Nuclear and Particle Physics > Week 1-5 > Flashcards

Week 1-5 Flashcards

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1
Q

What is spin?

A

Intrinsic angular momentum (this is restricted to certain values)

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2
Q

When will a particle be a boson (force particles) ?

A

When it has an integer spin

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3
Q

When will a particle be a fermion (matter particles) ?

A

When it has a half integer spin

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4
Q

What is the EM force mediated by?

A

By photons

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5
Q

What is charge?

A

It is a value which parametrises the amount of interaction

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6
Q

What does the strong force do?

A

Binds particles (quarks)

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7
Q

What does feel the strong force?

A

Leptons

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8
Q

If something something is coloured, what does it interact with?

A

The strong force

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9
Q

Which colours cancel each other out?

A

Mesons, quarks and anti quarks

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10
Q

What are gauge bosons?

A

Force carrying particles: photons, weak bosons and gluons

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11
Q

Which properties are conserved?

A

Electric charge, lepton number, baryon number, colour, quark flavour, energy, momentum and angular momentum

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12
Q

What violates flavour and strangeness?

A

Weak force

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13
Q

What is not conserved?

A

Spin and mass

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14
Q

What is an antiparticle?

A

A corresponding particle which has same mass and all other properties have same magnitude but OPPOSITE SIGN
They travel backwards in time (wrong way through time)

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15
Q

Why can’t the photon be detected?

A

It is virtual (exchange particle)

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16
Q

What is conserved at each interaction vertex?

A

Energy and momentum

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17
Q

What can charged particles do?

A

Emit a photon and reabsorb it, leading to a cloud of virtual photons around any charged particle.
This cloud’s density shows Coulomb’s law (inverse square law)

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18
Q

What is the strong nuclear force?

A

A strong attractive force which overcomes repulsion and it is felt in the nuclear radius (10^-14m) which is positively charged

it interacts between quarks

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19
Q

What is the range of the strong force?

A

It has a short range (found using change in x equation)

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20
Q

What is pion exchange?

A

Quark exchange

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21
Q

What are the characteristics of photons?

A

They must be off shell
They must be virtual
Give off the same pair as a result

22
Q

What does Pauli Exclusion require?

A

An extra degree of freedom

23
Q

What are the three distinct colours of each quark flavour?

A

Red, Blue, green

Colours are an extra way of labelling quarks that we have

24
Q

What do gluons couple to?

A

Colour and they carry colour (colour and anti colour)

25
Q

In EM why do charges form their field lines shape?

A

Due to photons which give rise to the field lines, they don’t interact with each other

26
Q

How is the strong force confined?

A

All field lines from one particle reach the other particle unlike EM

27
Q

What happens as a red and anti red are pulled apart?

A

Potential energy in system increases linearly due to the constant force and if they are pulled enough apart this will give them enough energy to create a new red and anti red particle which will be closer together

28
Q

When is the strong force weak?

A

When short distances are reached (inside a hadron)

29
Q

What is different about hadrons?

A

They are colourless (white) and they weigh more than their constituent quarks

30
Q

What does the weak force not conserve and why?

A

Do not conserve flavour as weak interactions are allowed between generations

31
Q

How is the W force worked out on a Feynman diagram?

A

Charge has to be conserved at each vertex to find which type is needed

32
Q

Why does the weak force not conserved strangeness?

A

Due to the cross generational types of interactions being allowed

33
Q

What impact parameter is expected to give the largest deflection in the alpha particle scattering?

A

When it is of order of the nucleus radius itself and will lead to a hyperbola path of electron

34
Q

When does the coulomb repulsion act?

A

When reasonably close to nucleus (small impact parameter b)

35
Q

How was the radius of the nucleus found?

A

Plotting the log of events against the scattering angle and the max angle found is the only non-rare event

36
Q

What does high energy scattering show?

A

Uniform charge density

37
Q

What does the nucleus consist of?

A

Protons and neutrons but behaves more like an incompressible fluid of nuclear material

38
Q

What are isobar nuclides?

A

Nuclides with the same mass/nucleon number (A)

39
Q

What are isotope nuclides?

A

Nuclides with the same number of protons (Z)

40
Q

What are isotone nuclides?

A

Nuclides with the same number of neutrons (N)

41
Q

What is the Valley of Stability?

A

Nuclides further from valley are less stable

42
Q

How much does binding energy account for in regards to mass?

A

Around 1 % of the mass

43
Q

Why are there “magic number” in regards to the more stable nuclei?

A

They have a higher binding energy than neighbours and lower mass than neighbours

44
Q

What kind of binding energy do most nuclides have?

A

Eb/A is around 8Mev

45
Q

What does the Liquid Drop Model dictate?

A

It gives three contributions to binding energy
Treats nucleus as drop of charged incompressible fluid
Nearest neighbour interactions only (plus Coulomb)

46
Q

What are the contributions of the Liquid drop model?

A

Volume term and surface term

Indicates that there are more interactions at the centre

47
Q

What is the Fermi Gas Model

A

It treats nucleons as independent non-interacting Fermi gases
They are free to move in spherically symmetric potential well
Discrete energy levels
Build up from ground state to Fermi energy

48
Q

What has a deep potential well?

A

Neutrons as there are typically more neutrons than protons even though they have the same fermi energy

49
Q

When is the binding energy per nucleon roughly constant?

A

When A is large

50
Q

What is fermi energy independent of?

A

The number of nucleons

51
Q

What can be assumed about heavy nuclei?

A

They don’t travel fast so no need to to use relativistic energy

52
Q

What does asymmetry mean?

A

Higher energy states (lower binding energy)

Nuclear and Particle Physics (2 decks)

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