3.2.1.5 - Classification of Particles Flashcards
What is a hadron?
Particles which feel the strong interaction.
What are hadrons made up of?
Smaller particles called quarks.
What are the two types of hadron?
Baryons and mesons.
What are protons and neutrons?
Baryons.
What are all baryons?
All baryons except protons decay into a proton.
What are the antiparticles of protons and neutrons?
Antibaryons.
What is interesting about antibaryons?
You don’t find them in ordinary matter.
What is the baryon number?
The number of baryons.
What are the baryon numbers of the proton and neutron?
+1
What is the baryon number of the antibaryon?
-1
If something isn’t a baryon what is its baryon number?
0
In an interaction what must the baryon number be?
Conserved.
What can you use the baryon number to predict?
Whether an interaction will happen.
What is the equation for neutron decay?
-
n -> p + e- + ν
What are all mesons?
Unstable and have a baryon number of 0.
What are pions?
The lightest mesons.
What are the three versions of pion?
π+, π-, π0
How are kaons different to pions?
They are heavier and more unstable than pions.
What do kaons decay into?
Pions
Where were kaons and pions discovered?
In cosmic rays.
What is a source of kaons and pions?
Cosmic ray showers.
How do mesons interact with baryons?
Via the strong interaction.
How are leptons different to hadrons?
They don’t feel the strong interaction.
How do leptons interact with other particles?
Using the weak interactions.
What are electrons?
Leptons and stable and familiar.
What are muons?
Unstable.
What do muons decay into?
Electrons.
What do both the muons and electrons also have?
Their own neutrino.
What do neutrinos have?
No mass, no charge
What is the Le of an electron?
+1
What is the Lu of a muon?
+1
What is the Le of a muon?
0
What is strangeness?
A quantum number so can only take a certain set of values.
Example of a strange particle?
Kaon.
When do strange particles decay and when are they created?
Decay - weak interaction.
Created - strong interaction
When is strangeness conserved?
Strong interaction.
What are strange particles always produced in?
Pairs.
How is strangeness conserved when they are produced as pairs?
One has a strangeness of +1 while the other has -1, therefore strangeness of 0.
How is a theory validated when discovering particles?
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.
Why is it hard to valiate the existence of a new particle?
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.
