Particle Physics

Question 1

What are the constituents of the atom?

Answer 1

Protons, neutrons and electrons

Question 2

What are the nucleons?

Answer 2

Protons and neutrons

Question 3

Where do electrons reside?

Answer 3

They orbit the nucleus in discrete energy shells.

Question 4

What are the different properties of protons, neutrons and electrons?

Answer 4

Question 5

What is specific charge?

Answer 5

Charge per unit mass

Question 6

What is the proton number denoted by?

Answer 6

Z

Question 7

What is the nucleon number denoted by?

Answer 7

A

Question 8

What are isotopes?

Answer 8

Atoms with the same number of protons but a different number or neutrons.

Question 9

What is strong nuclear force?

Answer 9

The force that acts between nucleons to counteract the electrostatic force of repulsion between protons.

Question 10

What is the range of strong nuclear force?

Answer 10

0 - 0.5 fm: repulsive
0.5 - 3 fm: attractive
>3 fm: no effect

Question 11

What causes nuclei to be unstable?

Answer 11

Too many protons, neutrons or both causing the strong nuclear force to be too weak to keep them stable and hence causing decay

Question 12

How do we know that neutrinos exist?

Answer 12

In beta decay, a neutrino must also be emitted alongside the beta particle, to conserve energy and lepton number

Question 13

What happens in pair production?

Answer 13

A high-energy gamma photon, when in contact with a nucleus, emits two particles in opposite directions - one particle as the antiparticle to the other.

Question 14

What is y-axis in Feynman diagram?

Answer 14

Time

Question 15

What are the leptons?

Answer 15

Electrons, muons, tauons and their corresponding neutrinos.

Question 16

What must be conserved in particle interactions?

Answer 16

1) Baryon number
2) Electron lepton number
3) Muon lepton number
4) Charge
5) Strangeness (only in strong interactions)
6) Energy and momentum

Question 17

What are the exchange particles and which forces do they correspond to?

Answer 17

1) Gluons - strong nuclear force
2) Virtual photons - electrostatic forces
3) W + / W - bosons - weak nuclear force (interactions where charge is not neutral)
4) Z bosons

Question 18

What are fermions?

Answer 18

Quarks and leptons

Question 19

What are the quarks?

Answer 19

• up, down, charm, strange, top, bottom
• antimatter equivalents

Question 20

What is the most stable quark and why?

Answer 20

• up quark
• higher mass means more unstable

Question 21

What is the range of electrostatic force?

Answer 21

Infinite

Question 22

What are the different types of hadrons and what are each of them made of?

Answer 22

1) Baryon - 3 quarks
2) Mesons - 2 quarks (1 quark and 1 antiquark)

Question 23

What are the types of baryons and what are they made of?

Answer 23

1) Proton - up up down
2) Neutron - up down down
3) Antiproton - antiup antiup antidown
4) Antineutron - antiup antidown antidown

up has charge 2/3
down has charge -1/3

Question 24

What is an antiparticle?

Answer 24

A particle with the same mass but opposite charge as the corresponding particle.

Question 25

What are the types of mesons and what quarks are they made of?

Answer 25

1) π+ - up antidown 2) π- - down antiup 3) π0 - up antiup or down antidown (exist for very short periods of time) 4) K+ - up anti-strange 5) K- - antiup strange 6) K0 - down anti-strange or antidown strange

Question 26

What occurs in annihilation?

Answer 26

When a particle and its corresponding particle interact, they produce two gamma rays that are emitted in opposite directions to conserve momentum. The energy of these gamma rays is dependent on the particles that are annihilated.

Question 27

What do leptons decay into?

Answer 27

- electrons are most stable - muons decay into electrons

Question 28

What occurs in alpha decay?

Answer 28

A large nuclei with too many **protons and neutrons** decays, emitting 2 protons and 2 neutrons

Question 29

What allows exchange particles to exert forces?

Answer 29

Momentum

Question 30

What occurs in beta-minus decay? What is the exchange particle?

Answer 30

A neutron decays into a proton, electron and electron antineutrino. It uses a W- boson.

Question 31

What is the Feynman diagram for beta-minus decay?

Answer 31

Question 32

What occurs in beta-plus decay? What is the exchange particle?

Answer 32

A proton decays into a neutron, positron and electron neutrino. It uses a W+ boson.

Question 33

What is the Feynman diagram for beta-plus decay?

Answer 33

Question 34

When do you use W- or W+ bosons?

Answer 34

W- when negative charge is being moved (e.g. an electron forms).

Question 35

What is usually on the left side of the Feynman diagram?

Answer 35

Baryons

Question 36

How do we represent exchange particles in a Feynman diagram and which exchange particle is it different for?

Answer 36

Gluons (SNF) are different and use spring-like line

Question 37

What happens in electron capture and what is the Feynman diagram for it?

Answer 37

A proton in the nucleus absorbs an electron and forms a neutron and electron neutrino.

Question 38

What happens in electron-proton collision and what is the Feynman diagram for it?

Answer 38

An electron collides with a proton, forming a neutron and electron neutrino.

Question 39

How would you show two electrons repelling each other with a Feynman diagram.

Answer 39

One electron on each side, virtual photon exchange particle and after they move away from each other.

Question 40

What is the other exchange particle for strong nuclear force?

Answer 40

Pions

Question 41

In which interaction is strange **not conserved**?

Answer 41

Weak nuclear force / decay

Question 42

What can strange change by if not conserved?

Answer 42

1 or -1

Question 43

What is the strangeness of a strange quark?

Answer 43

-1

Question 44

What is the charge of a strange quark?

Answer 44

-1/3