Chapter 2 - Quarks and Leptons

Question 1

What is a hadron?

Answer 1

A particle or antiparticle that can interact through the strong interaction and rest of the 4 fundamental interactions. A particle that consists of quarks or antiquarks.

Question 2

What are baryons?

What are examples of baryons?

Answer 2

Hadrons that decay into protons.
Baryons consist of 3 quarks.
Antibaryons consist of 3 antiquarks.
Protons and neutrons.

Question 3

What are mesons?

Answer 3

Hadrons that do not decay into protons.
They consist of a quark-antiquark pair.
Kaons and Pions.

Question 4

Rest energy of products =

Answer 4

Total energy before collision − Kinetic energy of products

Question 5

What are leptons?

Answer 5

Fundamental particles and antiparticles that do not interact through the strong interaction.
- Electron
- Muon
- Electron neutrino
- Muon neutrino
and respective antiparticles.

Question 6

What are the lepton numbers?

Answer 6

Lepton +1
Antilepton -1
Non-lepton 0

Question 7

What is the charge of the up, down and strange quarks?

Answer 7

u = +2/3
d = -1/3
s = -1/3

Antiquarks have opposite charges.

Question 8

What are the two types of neutrino?

Answer 8

Electron neutrino

Muon neutrino

Question 9

What is special about the Σ (sigma) and kaon particle?

Answer 9

They contain a strange or anti-strange quark.

Question 10

What is the baryon number of every quark?

Answer 10

+1/3

Question 11

What is the strangeness of a strange particle?

Answer 11

-1

Question 12

What is the only stable baryon into which other baryons eventually decay?

Answer 12

Proton

Question 13

What particles decay into pions?

Answer 13

Kaons

Question 14

What particle decays into an electron?

Answer 14

Muon

Question 15

What are strange particles?

Answer 15

Particles that are produced through the strong interaction and decay through the weak interaction.
They are always produced in pairs to conserve strangeness.

Question 16

What is the quark combination of a proton?

Answer 16

uud

Question 17

What is the quark combination of a neutron?

Answer 17

udd

Question 18

What is the strangeness of the up, down and strange quarks?

Answer 18

u = 0
d = 0
s = -1

Question 19

What is the exchange particle of the strong nuclear force?

Answer 19

Pion

Question 20

What are the baryon numbers?

Answer 20

Baryon +1
Anti-baryon -1
Non-baryon 0

Question 21

What quantities must be conserved in particle interactions?

Answer 21

• Energy
• Momentum
• Charge
• Lepton number
• Baryon number
• Strangeness (in a strong interaction only)

Question 22

What is the role of an exchange particle?

Answer 22

An exchange particle carries the force from one particle to another.
Exchange particles produce the effects of attraction and repulsion.

Question 23

SHOULD YOU REVISE KAON, PION AND MUON DECAY PATHS?

Answer 23

SHOULD YOU REVISE KAON, PION AND MUON DECAY PATHS?

Question 24

Does strangeness need to be conserved in weak interactions?

Answer 24

No, strangeness must only be conserved in strong interactions.
Strangeness can change by 0, +1, or -1 in weak interactions.

Question 25

Muons and electrons have different lepton numbers!

They both have to be conserved in particle interactions.

Answer 25

Muons and electrons have different lepton numbers!

They both have to be conserved in particle interactions.

Question 26

SPECIFICATION REQUIRES:
Appreciation that particle physics relies on the collaborative efforts of large teams of scientists and engineers to validate new knowledge.

Answer 26

SPECIFICATION REQUIRES:
Appreciation that particle physics relies on the collaborative efforts of large teams of scientists and engineers to validate new knowledge.

Question 27

Quark changes occur due to the…

Answer 27

Quark changes occur due to the weak interaction.