2.2 - Classification of Particles Flashcards
What are hadrons?
The group of subatomic particles that are made up of quarks.
What force do hadrons feel?
The strong nuclear force.
What are the 2 classes of hadrons?
Baryons
Mesons
What are baryons?
Particles made of 3 quarks (like protons and neutrons.)
What are mesons?
Particles made of a quark and anti-quark pair (like pions and kaons).
What are anti-baryons?
Anti-particles made of 3 anti-quarks (like anti-protons and anti-neutrons).
What are anti-mesons?
Anti-particles made of a quark and anti-quark pair (like anti-pions and anti-kaons).
What is a rule with quark combinations?
- only found in pairs of 3 quarks or 3 antiquarks.
- or found as a quark anti-quark pair
What is the baryon number?
The number of baryons in an interaction.
It must be conserved in all interactions.
What are the baryon numbers of different particles?
Baryons = +1
Anti-baryons = -1
Particles that aren’t baryons = 0
(baryon number must always be an integer)
What are the 3 types of quark?
up (u)
down (d)
strange (s)
What is the only stable baryon and why?
The proton because it has the longest half-life and is the lightest baryon.
What particle do all baryons eventually decay into?
The proton.
What is the lightest meson?
The pion.
What is particle exchange?
What is an exchange particle?
A virtual particle that mediates (bring about) the interaction between two other particles.
What are pions responsible for?
Binding nucleons together. (AKA the strong nuclear force).
Used as an exchange particle.
How are kaons produced?
By the strong interaction between pions and protons.
What do kaons decay into?
Pions.
Why do kaons have unusually long lifetimes?
They contain a strange quark.
What force do kaons decay through?
The weak interaction.
What are leptons?
A group of fundamental particles that aren’t made up of any other particles (like quarks).
What force do leptons interact with?
Weak, gravitational or electromagnetic.
What are the most common leptons?
- The electron
- The electron neutrino
- The muon
- The muon neutrino
What is heavier, the electron or the muon?
The muon.
Why aren’t quarks classed as leptons?
Leptons do not interact with the strong force whilst quarks do.
What is the lepton number of different particles? (L)
Leptons = +1
Anti-leptons = -1
Particles that aren’t leptons = 0
What do muons decay into?
Electrons.
What force does muon decay occur through?
The weak interaction.
What is the exchange particle of muon decay?
W⁻ boson.
Which group of particles are made of quarks?
All hadrons.
What are the 3 anti-quarks?
Anti-up
Anti-down
Anti-strange
What is the strangeness of all quarks and anti-quarks?
Up, down, anti-up and anti-down = 0
Strange = -1
Anti-strange = +1
What is the quark composition of a proton?
up, up, down
uud.
What is the quark composition of a neutron?
up, down, down
udd.
What is the quark composition of a π⁺?
up, anti-down.
u /d
What is the quark composition of a π⁻?
Anti up, down.
/u d
What is the quark composition of a π⁰?
up, anti-up
OR
down, anti-down
u /u
d /d
What is the quark composition of a K⁺?
up, anti-strange
u /s
What type of quark do all kaons have?
A strange or anti strange quark.
What is the quark composition of a K⁻?
anti-up, strange
/u s
What is the quark composition of a K⁰?
Anti-down, strange
OR
down, anti-strange
/d s
d /s
What are 3 properties of strange particles?
- Produced through the strong interaction
- Decay through the weak interaction
- Produced in quark-antiquark pairs
What is the exchange particle of the weak interaction?
W⁺ boson.
(eg - kaon decay)
Where is strangeness not conserved?
Through the weak interaction.
What are 2 reasons why particle accelerators used to collide particles at high speeds?
- To produce new particles
- Reveal the inner structure of particles
