4. Hadrons and Leptons

Question 1

What makes a particle a Hadron?

Answer 1

Hadrons are particles that are affected by the Strong Nuclear Force

Question 2

What makes up Hadrons?

Answer 2

Hadrons are not fundamental particles, instead they are made up of smaller particles known as quarks.

Question 3

What are the two classes of Hadrons?

Answer 3

Hadrons are made up of two classes known as Baryons and Mesons.

Question 4

What particles are classed as Baryons?

Answer 4

The proton and neutron are baryons.

Question 5

What is the only stable baryon?

Answer 5

Only the Proton is stable, this means that eventually, all baryons decay into protons.

Question 6

What are antibaryons?

Answer 6

Antibaryons are just the antiparticles of protons and neutrons, but as they are annihilated when they meet their corresponding particle, you cannot find them in ordinary matter.

Question 7

What is a Baryon number?

Answer 7

A baryon number is a quantum number that must be conserved. It is just the number of baryons within a particle.

Question 8

How are baryon numbers added?

Answer 8

The protons and neutrons (as well as other baryons) each have a baryon number of +1
Antibaryons have a baryon number of -1
Particles which are not Baryons or Antibaryons have a baryon number of 0

Question 9

How can baryon numbers be used to predict if an interaction can happen?

Answer 9

Baryon number can be used to determine this as the baryon number will never change, so if the baryon number changes within an interaction, the interaction is not possible.

Question 10

What interaction causes Beta decay?

Answer 10

Beta decay is caused by the weak interaction?

Question 11

What happens during Beta decay?

Answer 11

During Beta decay a neutron decays to form a proton, an electron and an antineutrino.

Question 12

What are Mesons?

Answer 12

Mesons interact with baryons via the strong force, all of them are unstable and have baryon number B = 0

Question 13

What particles are Mesons?

Answer 13

Pions and Kaons are known as mesons, although these particles can be split up into their charges, as there are negative, neutral and positive Pions & kaons, although the negative is just the antiparticle of the positive.

Question 14

What are Pions?

Answer 14

Pions are the lightest mesons, they have 3 versions, each with different electrical charges (positive, Neutral and negative)
THe negative Pion is the anti particle of the positive pion, whereas the neutral pion is an antiparticle of itself.
They are the exchange particle for the Strong Nuclear Force

Question 15

What are Kaons?

Answer 15

Kaons are heavier and more unstable than pions, they also have positive, negative and neutral forms, and they have a very short lifetime and decay into pions.

Question 16

How are mesons detected?

Answer 16

Mesons can be made visible within a cloud chamber, but can be detected by placing two geiger counters on top of each other separating them with absorbing lead, if both detect radiation simultaneously, they are detecting a ray of pions and kaons.

Question 17

What are Leptons?

Answer 17

Leptons are fundamental particles that don’t feel the strong nuclear force and only interact via the Weak nuclear force, Gravitational force, and the electromagnetic force if they are charged.

Question 18

What particles are leptons?

Answer 18

Electrons, Electron neutrinos, muons and muon neutrinos are leptons

Question 19

What are Muons

Answer 19

Muons are like heavy electrons, but they are unstable and eventually decay into electrons.

Question 20

What are Lepton Numbers?

Answer 20

Lepton Numbers are QUantum numbers like baryon numbers, they must be conserved, but there are two different types, Le and Lu, the electron and electron neutrino and +1 Le, whereas the Muon and Muon neutrino have +1 Lu