2.2 - Classification of Particles

Question 1

What are hadrons?

Answer 1

The group of subatomic particles that are made up of quarks.

Question 2

What force do hadrons feel?

Answer 2

The strong nuclear force.

Question 3

What are the 2 classes of hadrons?

Answer 3

Baryons
Mesons

Question 4

What are baryons?

Answer 4

Particles made of 3 quarks (like protons and neutrons.)

Question 5

What are mesons?

Answer 5

Particles made of a quark and anti-quark pair (like pions and kaons).

Question 6

What are anti-baryons?

Answer 6

Anti-particles made of 3 anti-quarks (like anti-protons and anti-neutrons).

Question 7

What are anti-mesons?

Answer 7

Anti-particles made of a quark and anti-quark pair (like anti-pions and anti-kaons).

Question 8

What is a rule with quark combinations?

Answer 8

• only found in pairs of 3 quarks or 3 antiquarks.
• or found as a quark anti-quark pair

Question 9

What is the baryon number?

Answer 9

The number of baryons in an interaction.
It must be conserved in all interactions.

Question 10

What are the baryon numbers of different particles?

Answer 10

Baryons = +1
Anti-baryons = -1
Particles that aren’t baryons = 0
(baryon number must always be an integer)

Question 11

What are the 3 types of quark?

Answer 11

up (u)
down (d)
strange (s)

Question 12

What is the only stable baryon and why?

Answer 12

The proton because it has the longest half-life and is the lightest baryon.

Question 13

What particle do all baryons eventually decay into?

Answer 13

The proton.

Question 14

What is the lightest meson?

Answer 14

The pion.

Question 15

What is particle exchange?

Question 16

What is an exchange particle?

Answer 16

A virtual particle that mediates (bring about) the interaction between two other particles.

Question 17

What are pions responsible for?

Answer 17

Binding nucleons together. (AKA the strong nuclear force).
Used as an exchange particle.

Question 18

How are kaons produced?

Answer 18

By the strong interaction between pions and protons.

Question 19

What do kaons decay into?

Answer 19

Pions.

Question 20

Why do kaons have unusually long lifetimes?

Answer 20

They contain a strange quark.

Question 21

What force do kaons decay through?

Answer 21

The weak interaction.

Question 22

What are leptons?

Answer 22

A group of fundamental particles that aren’t made up of any other particles (like quarks).

Question 23

What force do leptons interact with?

Answer 23

Weak, gravitational or electromagnetic.

Question 24

What are the most common leptons?

Answer 24

• The electron
• The electron neutrino
• The muon
• The muon neutrino

Question 25

What is heavier, the electron or the muon?

Answer 25

The muon.

Question 26

Why aren't quarks classed as leptons?

Answer 26

Leptons do not interact with the strong force whilst quarks do.

Question 27

What is the lepton number of different particles? (L)

Answer 27

Leptons = +1 Anti-leptons = -1 Particles that aren't leptons = 0

Question 28

What do muons decay into?

Answer 28

Electrons.

Question 29

What force does muon decay occur through?

Answer 29

The weak interaction.

Question 30

What is the exchange particle of muon decay?

Answer 30

W⁻ boson.

Question 31

Which group of particles are made of quarks?

Answer 31

All hadrons.

Question 32

What are the 3 anti-quarks?

Answer 32

Anti-up Anti-down Anti-strange

Question 33

What is the strangeness of all quarks and anti-quarks?

Answer 33

Up, down, anti-up and anti-down = 0 Strange = -1 Anti-strange = +1

Question 34

What is the quark composition of a proton?

Answer 34

up, up, down uud.

Question 35

What is the quark composition of a neutron?

Answer 35

up, down, down udd.

Question 36

What is the quark composition of a π⁺?

Answer 36

up, anti-down. u /d

Question 37

What is the quark composition of a π⁻?

Answer 37

Anti up, down. /u d

Question 38

What is the quark composition of a π⁰?

Answer 38

up, anti-up OR down, anti-down u /u d /d

Question 39

What is the quark composition of a K⁺?

Answer 39

up, anti-strange u /s

Question 40

What type of quark do all kaons have?

Answer 40

A strange or anti strange quark.

Question 41

What is the quark composition of a K⁻?

Answer 41

anti-up, strange /u s

Question 42

What is the quark composition of a K⁰?

Answer 42

Anti-down, strange OR down, anti-strange /d s d /s

Question 43

What are 3 properties of strange particles?

Answer 43

- Produced through the strong interaction - Decay through the weak interaction - Produced in quark-antiquark pairs

Question 44

What is the exchange particle of the weak interaction?

Answer 44

W⁺ boson. (eg - kaon decay)

Question 45

Where is strangeness not conserved?

Answer 45

Through the weak interaction.

Question 46

What are 2 reasons why particle accelerators used to collide particles at high speeds?

Answer 46

- To produce new particles - Reveal the inner structure of particles