Quarks and Leptons

Question 1

Describe a muon and what it decays into

Answer 1

It is a heavy electron (over 200 times the rest mass). Negatively charged. Decays into an electron and antineutrino. Antimuon decays into positron and neutrino.

Question 2

Describe a pi meson and what it decays into

Answer 2

Has rest mass greater than muon but less than a proton. Can be positive, negative or neutral. Charged pions can decay into a muon and antineutrino or an antimuon and neutrino. Neutral one just decays into high energy photons.

Question 3

Describe a k-meson and what it decays into

Answer 3

Has a rest mass greater than a pion but less than a proton. Can be positive, negative or neutral. Can decay into pions, or a muon and antineutrino, or an antimuon and neutrino. It contains a strange or antistrange quark.

Question 4

Define leptons

Answer 4

Particles and antiparticles that interact through the weak force, the gravitational force and the electromagnetic force if charged.

Question 5

Define hadrons

Answer 5

Particles and antiparticles that interact through the strong force as well as the other three fundamental forces.

Question 6

Define baryons

Answer 6

Protons and other hadrons that decay into protons either directly or indirectly. Made of three quarks.

Question 7

Define mesons

Answer 7

Hadrons that do not include protons in their decay products. Made of a quark and antiquark pair.

Question 8

What is in the electron branch of leptons?

Answer 8

Electrons, electron neutrinos and their antiparticles

Question 9

What is in the muon branch of leptons?

Answer 9

Muons, muon neutrinos and their antiparticles

Question 10

How can leptons produce hadrons?

Answer 10

If a lepton interacts with an anti lepton they annihilate. This event produces a quark and corresponding antiquark which move away in opposite directions, producing a shower of hadrons in each direction.

Question 11

What is always conserved in interactions involving leptons?

Answer 11

Charge, electron lepton number, muon lepton number, energy

Question 12

Charge and strangeness of up, down and strange quarks

Answer 12

Up- +2/3 0
Down- -1/3 0
Strange- -1/3 -1
Opposite values for all antimatter

Question 13

What is a sigma particle?

Answer 13

A baryon containing a strange quark

Question 14

When is the baryon number conserved?

Answer 14

In strong interactions

Question 15

When is strangeness conserved?

Answer 15

In strong interactions

Question 16

Through which interactions are strange particles produced and decay?

Answer 16

Produced in pairs through the strong interaction. Decay through the weak interaction.

Question 17

What happens to overall strangeness in weak interactions?

Answer 17

Can change by 1 or isn’t changed