9. The Standard Model of Particle Physics

Question 1

What theory is used to describe the electromagnetic and weak interaction in the standard model?

Answer 1

The electroweak theory

Question 2

What theory us used to describe strong interactions in the standard model?

Answer 2

Quantum chromodynamics (QCD)

Question 3

What are the basic constituents of matter?

Answer 3

Quarks and leptons

Question 4

What is the spin of a quark?

Answer 4

1/2

Question 5

What is the spin of a lepton?

Answer 5

1/2

Question 6

Quarks come in _ flavours and _ colours.

Answer 6

6
3

Question 7

What are the 6 flavours of quark?

Answer 7

Up
Down
Strange
Charm
Top
Bottom

Question 8

Leptons come in _ types.

Answer 8

6

Question 9

How do quarks and leptons interact?

Answer 9

Via the spin-1 (gauge) boson

Question 10

Quarks and leptons are subdivided into _ generations based on ____.

Answer 10

3
Mass

Question 11

What are the 4 fundamental forces?

Answer 11

• Gravity
• Weak nuclear
• Electromagnetic
• Strong nuclear

Question 12

How do the 4 fundamental forces act?

Answer 12

By the exchange particles (or force carriers) associated with them.

Question 13

Which of the 4 fundamental forces is not part of the standard model? Why?

Answer 13

Gravity as it doesn’t have a quantum theory

Question 14

Rank the 4 fundamental forces from weakest to strongest

Answer 14

1. Gravity
2. Weak force
3. Electromagnetism
4. Strong force

Question 15

What does gravity act between?

Answer 15

All objects with mass

Question 16

What does the weak force do?

Answer 16

It governs particle decay

Question 17

What does electromagnetism act between?

Answer 17

Electrically charged particles

Question 18

What does the strong force do?

Answer 18

Binds quarks together

Question 19

Which particles experience gravity?

Answer 19

All particles with mass

Question 20

Which particles experience the weak force?

Answer 20

Quarks and leptons

Question 21

Which particles experience electromagnetism?

Answer 21

Electrically charged particles

Question 22

Which particles experience the strong force?

Answer 22

Quarks and gluons

Question 23

What is the force carrier particle for gravity?

Answer 23

Graviton (not yet observed)

Question 24

What is the force carrier particle for the weak force?

Answer 24

W+, W-, Z0 (W and Z)

Question 25

What is the force carrier particle for electromagnetism?

Answer 25

γ (photon)

Question 26

What is the force carrier particle for the strong force?

Answer 26

g (gluon)

Question 27

What is the range of gravity?

Answer 27

Infinite

Question 28

What is the range of the weak force?

Answer 28

Short range

Question 29

What is the range of electromagnetism?

Answer 29

Infinite

Question 30

What is the range of the strong force?

Answer 30

Short range

Question 31

What is a gluon?

Answer 31

A massless force carrier particle with a property called colour confinement.

Question 32

What does gravity give rise to?

Answer 32

- Newton's Law - General relativity

Question 33

Give the equation for Newton's law of gravity

Answer 33

F = force G = gravitational constant M = mass 1 m = mass 2 r = separation distance

Question 34

What spin does the (hypothetical) graviton have?

Answer 34

2

Question 35

What mass does the (hypothetical) graviton have?

Answer 35

0

Question 36

Where is the weak nuclear force most commonly seen?

Answer 36

Nuclear beta decay

Question 37

_____________ only interact via the weak force.

Answer 37

Neutrino's

Question 38

What spin do gauge bosons (W and Z) have?

Answer 38

1

Question 39

What mass do gauge bosons (W and Z) have?

Answer 39

Large mass: ~80 GeV/c²

Question 40

Give the equation that describes how the weak force varies with distance

Answer 40

q = charge r = separation distance M_W = gauge boson mass

Question 41

What does electromagnetism give rise to?

Answer 41

The Coulomb force

Question 42

Give the equation for the Coulomb force

Answer 42

F = force K = constant q = charge r = separation distance

Question 43

What is electromagnetism governed by?

Answer 43

Maxwell's laws

Question 44

What is the spin of a photon?

Answer 44

1

Question 45

What is the mass of a photon?

Answer 45

0

Question 46

A photon is a type of _____ _____.

Answer 46

Gauge boson

Question 47

What is the purpose of the strong nuclear force?

Answer 47

To keep nucleons bound

Question 48

Nucleons are made up of ______.

Answer 48

Quarks

Question 49

What is the spin of a gluon?

Answer 49

1

Question 50

What is the mass of a gluon

Answer 50

0

Question 51

Why doesn't the strong nuclear force have infinite range?

Answer 51

Because quarks and gluons carry a type of charge called colour so are limited to short range by colour confinement.

Question 52

What spin do fermions have?

Answer 52

1/2

Question 53

Do fermions obey the Pauli exclusion principle?

Answer 53

Yes

Question 54

State the 2 main types of fermions

Answer 54

- Leptons - Baryons (electrons, neutrinos, protons, neutrons)

Question 55

The fermion wavefunction is ___________ under the exchange of two identical particles.

Answer 55

Anti-symmetric

Question 56

What spin do bosons have?

Answer 56

Integer

Question 57

Give one example of a type of boson

Answer 57

Force carriers

Question 58

The boson wavefunction is _________ under the exchange of two identical particles.

Answer 58

Symmetric

Question 59

Are all particles in the standard model identical?

Answer 59

Yes

Question 60

Define quantum field theory

Answer 60

The theory that there is one field for each particle for the entire universe. Particles are (quantized) excitations of this field.

Question 61

Are leptons bosons or fermions?

Answer 61

Fermions

Question 62

What are the 6 flavours of lepton?

Answer 62

First generation: electron (e) and electron neutrino (v_e) Second generation: muon (µ) and muon neutrino (v_µ) Third generation: tau (τ) and tau neutrino (τ)

Question 63

What is the charge of an electron?

Answer 63

-1 e

Question 64

What is the charge of an electron neutrino?

Answer 64

0

Question 65

What is the charge of a muon?

Answer 65

-1 e

Question 66

What is the charge of a muon neutrino?

Answer 66

0

Question 67

What is the charge of a tau particle?

Answer 67

-1 e

Question 68

What is the charge of a tau neutrino?

Answer 68

0

Question 69

Which is heaviest: the electron, the muon, or the tau particle?

Answer 69

1. Tau 2. Muon 2. Electron

Question 70

Are quarks bosons or fermions?

Answer 70

Fermions

Question 71

What is the charge of a down quark?

Answer 71

-1/3 e

Question 72

What is the charge of a charm quark?

Answer 72

2/3 e

Question 72

What is the charge of an up quark?

Answer 72

2/3 e

Question 72

What is the charge of a bottom quark?

Answer 72

-1/3 e

Question 73

What is the charge of a strange quark?

Answer 73

-1/3 e

Question 74

What is the charge of a top quark?

Answer 74

2/3 e

Question 75

Sort the 6 quark flavours into generations

Answer 75

First generation: d, u Second generation: s, c Third generation: b, t

Question 76

What are the 3 colours of quark?

Answer 76

Red, green, blue

Question 77

Why can't free quarks be observed?

Answer 77

Because coloured objects cannot be observed.

Question 78

What are the two types of colourless states?

Answer 78

Baryons: states with 3 quarks of each of the different colours (red + green + blue = white = colourless) Mesons: states with 2 quarks with a colour-anticolour quark pair (red+anti-red = colourless)

Question 79

Which generation of leptons and quarks is most common in nature? Why?

Answer 79

First generation because they are lightest

Question 80

What charge do gluons have?

Answer 80

0

Question 81

What charge do photons have?

Answer 81

0

Question 82

What charge do W± force carriers have?

Answer 82

±1

Question 83

What charge do Z0 force carriers have?

Answer 83

0

Question 84

Gluons, photons, W±, and Z0 force carriers are spin-_ _______.

Answer 84

1 Bosons

Question 85

What force do gluons mediate?

Answer 85

Strong nuclear

Question 86

What force do photons mediate?

Answer 86

Electromagnetism

Question 87

What force do W± force carriers mediate?

Answer 87

Weak nuclear

Question 88

What force do Z0 force carriers mediate?

Answer 88

Weak nuclear

Question 89

Describe the Higgs Boson (H0)

Answer 89

It is the only spin-0 boson in the standard model. It has no electric or colour charge. Its purpose is to allow W and Z bosons (and other fermions) to acquire mass via the Higgs mechanism.

Question 90

What is the mass of the Higgs Boson?

Answer 90

125 GeV/c²

Question 91

All particles have ____-_________ with opposite charge and baryon/lepton/colour/quark flavour number.

Answer 91

Anti-particles

Question 92

What are hadrons?

Answer 92

Particles composed of quarks

Question 93

What are the two types of hadron?

Answer 93

- Baryons - Mesons

Question 94

How many quarks to baryons have?

Answer 94

3

Question 95

Give 2 examples of baryons

Answer 95

- Protons - Neutrons

Question 96

________ are the only stable baryon.

Answer 96

Protons

Question 97

How many quarks do mesons have?

Answer 97

2 as a quark/anti-quark pair

Question 98

Are there any stable mesons?

Answer 98

No, they quickly decay into leptons and photons

Question 99

Give 2 examples of mesons

Answer 99

- Pion - Kaon

Question 100

State the 3 types of pion

Answer 100

Question 101

State the 3 types of kaon

Answer 101