Chapter 2 - Quarks and Leptons

Question 1

What are the 4 leptons?

Answer 1

Electron
Electron neutrino
Muon
Muon neutrino

Question 2

Leptons

Answer 2

Fundamental particles, no internal structure
All have lepton number as +-1
Baryon number and strangeness 0
Neutrinos have no charge
Can exist alone
Interact by the weak and electromagnetic interaction

Question 3

Hadrons

Answer 3

Not fundamental as all contain quarks which never exist more
Lepton number of 0
Baryons and mesons
Interact by the strong, weak, and electromagnetic interaction

Question 4

Quarks

Answer 4

Baryon number of 1/3
Up - charge of +2/3
Down - charge of -1/3
Strange - charge of -1/3
Opposite for anti-quarks

Question 5

The 3 quarks

Answer 5

Up, down, strange

Question 6

Baryons

Answer 6

Made up of 3 quarks
Baryon number of +-1
Lepton number and strangeness 0

Question 7

The 2 baryons

Answer 7

Neutron = ddu
Proton = uud

Question 8

Mesons

Answer 8

Kaons and pions
Made up of one quark and one antiquark
Baryon and lepton number = 0
Mesons decay into photons and leptons

Question 9

Kaons

Answer 9

Kaons decay into pions
Kaons all have a strange or antistrange quark
K0 = down, antistrange
K+ = up, antistrange
K- = antiup, strange

Question 10

Pions

Answer 10

Decay into photons and leptons
The exchange particle for the strong nuclear force between baryons
Pi- = down, anti up
Pi0 = up, anti up
Pi0 = down, anti down
Pi+ = up, anti down

Question 11

Electric charge of particles

Answer 11

To make a particle, the charges of the individual quarks must add up to make a whole number. Particles cannot have a fractional charge.

Question 12

Muons decay into?

Answer 12

Electron

Question 13

What is the only stable baryon?

Answer 13

Proton

Question 14

What are the stable leptons?

Answer 14

Electron, electron neutrino

Question 15

Strange particles

Answer 15

Created by the strong nuclear interaction, decay via the weak nuclear interaction
Always creased in pairs
Have unusually long lifetimes

Question 16

Charged pions decay into?

Answer 16

Muons and neutrino

Question 17

Hadrons decay?

Answer 17

Via the weak nuclear interaction

Question 18

Which properties are always conserved?

Answer 18

Lepton number
Baryon number
Charge

Question 19

Strangeness

Answer 19

Conserved in strong interactions but can change by 0, -1, +1 in weak interactions

Question 20

Rest energy

Answer 20

Energy equivalence of the particles mass

Question 21

Lifetime of most particles?

Answer 21

Most particles are unstable and only have short lifetimes (x10^-18

Question 22

Weak interaction:

Answer 22

Strangeness not conserved
Lepton decays -> muon to electron
A change in one quark type

Question 23

Strong interaction:

Answer 23

Quarks just rearranged
Pair production
- strange quarks produced in pairs
- kaons produced
- pions produced