3.2.1.5 - Classification of Particles

Question 1

What is a hadron?

Answer 1

Particles which feel the strong interaction.

Question 2

What are hadrons made up of?

Answer 2

Smaller particles called quarks.

Question 3

What are the two types of hadron?

Answer 3

Baryons and mesons.

Question 4

What are protons and neutrons?

Answer 4

Baryons.

Question 5

What are all baryons?

Answer 5

All baryons except protons decay into a proton.

Question 6

What are the antiparticles of protons and neutrons?

Answer 6

Antibaryons.

Question 7

What is interesting about antibaryons?

Answer 7

You don’t find them in ordinary matter.

Question 8

What is the baryon number?

Answer 8

The number of baryons.

Question 9

What are the baryon numbers of the proton and neutron?

Answer 9

+1

Question 10

What is the baryon number of the antibaryon?

Answer 10

-1

Question 11

If something isn’t a baryon what is its baryon number?

Answer 11

0

Question 12

In an interaction what must the baryon number be?

Answer 12

Conserved.

Question 13

What can you use the baryon number to predict?

Answer 13

Whether an interaction will happen.

Question 14

What is the equation for neutron decay?

Answer 14

-

n -> p + e- + ν

Question 15

What are all mesons?

Answer 15

Unstable and have a baryon number of 0.

Question 16

What are pions?

Answer 16

The lightest mesons.

Question 17

What are the three versions of pion?

Answer 17

π+, π-, π0

Question 18

How are kaons different to pions?

Answer 18

They are heavier and more unstable than pions.

Question 19

What do kaons decay into?

Answer 19

Pions

Question 20

Where were kaons and pions discovered?

Answer 20

In cosmic rays.

Question 21

What is a source of kaons and pions?

Answer 21

Cosmic ray showers.

Question 22

How do mesons interact with baryons?

Answer 22

Via the strong interaction.

Question 23

How are leptons different to hadrons?

Answer 23

They don’t feel the strong interaction.

Question 24

How do leptons interact with other particles?

Answer 24

Using the weak interactions.

Question 25

What are electrons?

Answer 25

Leptons and stable and familiar.

Question 26

What are muons?

Answer 26

Unstable.

Question 27

What do muons decay into?

Answer 27

Electrons.

Question 28

What do both the muons and electrons also have?

Answer 28

Their own neutrino.

Question 29

What do neutrinos have?

Answer 29

No mass, no charge

Question 30

What is the Le of an electron?

Answer 30

+1

Question 31

What is the Lu of a muon?

Answer 31

+1

Question 32

What is the Le of a muon?

Answer 32

0

Question 33

What is strangeness?

Answer 33

A quantum number so can only take a certain set of values.

Question 34

Example of a strange particle?

Answer 34

Kaon.

Question 35

When do strange particles decay and when are they created?

Answer 35

Decay - weak interaction.

Created - strong interaction

Question 36

When is strangeness conserved?

Answer 36

Strong interaction.

Question 37

What are strange particles always produced in?

Answer 37

Pairs.

Question 38

How is strangeness conserved when they are produced as pairs?

Answer 38

One has a strangeness of +1 while the other has -1, therefore strangeness of 0.

Question 39

How is a theory validated when discovering particles?

Answer 39

Results from different experiments are combined to try and confirm the new particle. When the theory is more likely to be correct and the scientific community start to accept it - it is validated.

Question 40

Why is it hard to valiate the existence of a new particle?

Answer 40

Experiments in particle physics often need particles traveling at incredibly high speeds. This can only be achieved using particle accelerators which are expensive to build and run. They also require large groups do scientists and engineers from all over the world.