3.2.1.5 Classification of Particles

Question 1

What is a hadron?

Answer 1

A hadron is a particle that feels the strong nuclear force, or interacts through the strong interaction.

Question 2

Are hadrons fundamental?

Answer 2

Hadrons are not fundamental as they are made of quarks.

Question 3

What are the two types of hadrons?

Answer 3

The two types of hadrons are baryons and mesons.

Question 4

What are baryons?

Answer 4

Baryons are hadrons which are made up of three quarks.

Question 5

What are the two baryons?

Answer 5

The two baryons are the proton and the neutron.

Question 6

Which baryon is stable? What do all baryons eventually decay into?

Answer 6

The proton is the most stable baryon. All baryons except the proton are unstable.
All baryons except protons eventually decay into protons.

Question 7

What is an antibaryons?

Answer 7

An antibaryon is the opposite of a baryon. For example antiprotons and antineutrons.

Question 8

Why are antibaryons not found in ordinary matter?

Answer 8

Antibaryons are not found in ordinary matter because they are annihilated when they meet the corresponding particle.

Question 9

What is the baryon number?

Answer 9

The baryon number is a quantum number that tells us the number of baryons.

Question 10

What is the baryon number of some common particles?

Answer 10

The baryon number of all baryons is + 1.
The baryon number of all antibaryons is - 1.
The baryon number of all other particles is 0.

Question 11

What are mesons?

Answer 11

Mesons are another type of hadron which are composed of a quark and an antiquark.

Question 12

Are all mesons stable?

Answer 12

All mesons are unstable and have a baryon number of 0.

Question 13

What are the two types of mesons?

Answer 13

The two types of mesons are kaons (symbol K) and pions (symbol pi).

Question 14

What are the three types of kaon?

Answer 14

The three types of kaon are:
Kaon +
Kaon 0
Kaon -

Question 15

What are the three types of pions?

Answer 15

Pion +
Pion 0
Pion -

Question 16

What is the difference between kaons and pions?

Answer 16

Pions are lighter than mesons, whereas kaons are heaver and more unstable.
Kaons have a very short lifetime.
Kaons decay into pions.

Question 17

How do mesons and baryons interact?

Answer 17

Mesons and baryons interact via the strong force.

Question 18

What are leptons? Are they fundamental?

Answer 18

Leptons are particles which do not experience the nuclear strong force.
Leptons are fundamental particles.

Question 19

How do leptons interact?

Answer 19

They only interact via the weak interaction.

Question 20

What the two types of lepton?

Answer 20

The two types of leptons are muons and electrons.

Question 21

What are the anti-leptons?

Answer 21

Anti-leptons are the antiparticle equivalent of leptons.

Question 22

Are electrons stable, and are muons stable?

Answer 22

Electrons are stable and muons are heavy electrons which are unstable.

Question 23

What do muons decay into?

Answer 23

Muons eventually decay into electrons.

Question 24

What are the two types of lepton neutrino?

Answer 24

The electron Neutrino Ve

The muon Neutrino Vµ.

Question 25

What do neutrinos have?

Answer 25

Neutrinos have zero mass, and zero electric charge.

Question 26

What is the lepton number?

Answer 26

Lepton number is a quantum number which shows how many leptons a particle has.

Question 27

What is the lepton number of a lepton and an anti-lepton?

Answer 27

Lepton number of a lepton = + 1 | Lepton number of an anti-lepton = - 1

Question 28

What are the two types of lepton numbers?

Answer 28

The two types of lepton number are muon lepton number and electron lepton number, which must be counted seperately.

Question 29

What is the charge of a muon?

Answer 29

The charge of a muon is -1.

Question 30

What are the charges of electron and muon neutrinos?

Answer 30

The charges on both are 0.

Question 31

What is the Le number of each lepton.

Answer 31

``` Electron = + 1 Position = - 1 Electron Neutrino = + 1 Anti Electron Neutrino = - 1 All the rest have 0 ```

Question 32

What is the Lµ number of each of the leptons.

Answer 32

``` Muon = + 1 Antimuon = - 1 Muon Neutrino = + 1 Anti Muon Neutrino = -1 All the rest have 0 ```

Question 33

What is strangeness?

Answer 33

Strangeness is a quantum number.

Question 34

Which particles are strange?

Answer 34

Only kaons are strange particles.

Question 35

How are strange particles created and decayed?

Answer 35

Strange particles are created via the strong interaction, and decay via the weak interaction. Strange particles are always produced in pairs.

Question 36

What is the rule for conservation of strangeness?

Answer 36

Strangeness is conserved in the strong interaction, but not in the weak interaction. They can change by +/- 1 in the weak interaction.

Question 37

What is the strangeness of the kaons?

Answer 37

K+ = +1 K0 = +1 K- = -1 Anti K0 = -1

Question 38

Pions are the exchange particle for what?

Answer 38

Pions are the exchange particle for the strong nuclear force.

Question 39

What is the definition of the strange particles?

Answer 39

Strange particles are particles that are produced through the strong interaction and decay through the weak interaction (eg kaons).