P2: Quarks and Leptons

Question 1

What is the order of classification of subatomic particles?

Answer 1

All matter can be split into either Hadrons (which are affected by the strong force) or Leptons (which aren’t).
Hadrons can then be further split into Baryons (which are or decay into protons) or Mesons (whose decay products do not include protons).

Question 2

Mesons are…?

Answer 2

Particles with 2 quarks (1 quark, 1 antiquark) who cannot decay into protons e.g kaons or pions.

Question 3

Baryons are…?

Answer 3

Particles with 3 quarks, e.g protons, neutrons or sigma particles, which are already or will decay into protons.

Question 4

What’s in a sigma baryon?

Answer 4

E+ = uus
Eo = uds
E- = dds

Question 5

Give the 2 sets of leptons. (particles + antiparticles)

Answer 5

particles (with lepton no. +1): electrons, muons, electron neutrinos and muon neutrionos.
antiparticles (lepton no. -1): positrons, antimuons , electron antineutrinos and muon antineutrinos.

Question 6

What is the key difference between hadrons and leptons?

Answer 6

Whilst hadrons can experience and of the four fundamental forces, leptons can only experience 3, with the exception of the strong nuclear force.

Question 7

What are other names for a B+/B- particle?

Answer 7

Antineutrino or Positron

Question 8

What Baryon number does a quark have?

Answer 8

+1/3 (quarks)
or -1/3 (antiquarks)

Question 9

Why are Up and Down quarks more common than others?

Answer 9

They are the lightest quarks.

Question 10

Do neutrinos have mass?

Answer 10

Yes - negligible mass.