- these are particles and antiparticles which interact through the strong nuclear force (e.g. protons, neutrons, Pi mesons and K mesons)
- Unlike a particle like an electron, hadrons are NOT fundamental particles because they are made up of smaller particles called quarks.
- There are two types of hadrons:
1. Baryons - protons and all other hadrons that decay into protons, directly or indirectly
2. Mesons: hadrons that do not decay into protons
* Baryon number - the number of baryons. All baryons have a baryon number of +1. All antibaryons have a baryon number of -1. Particles that aren't baryons are 0.
- muon: (heavy electron) ų, a negatively charged particle with a rest mass 200x of an electron
- pion: Pi+, Pi- and Pi0. Have a rest mass GREATER than a muon but less than a proton.
- kaon: (K meson) can be +, - or neutral with a rest mass GREATER than a pion but less than a proton. they decay through the weak interaction but are created through the strong force.
- fundamental particles that interact through the weak nuclear force and the EM force if charged.
- electrons are stable leptons.
- muons are heavier, unstable versions of electrons, which eventually decay into electrons or e+
- these particles each have their own neutrinos, which only take part in weak interaction.
Quarks and Antiquarks
- quarks are fundamental particles: up, down, strange, charm, top and bottom
- baryons are made up of 3 quarks and anti baryons of 3 antiquarks
- mesons as made up of quark-antiquark pair. Pions are made up of up, down, anti up and anti down. Kaons are made up of strange quarks as well.
Quark and beta decay:
- in beta minus decay - a NEUTRON in a neutron rich nucleus changes into a proton, releasing an electron and an electron antineutrino. Quarks: d --> u
- in beta plus decay - a PROTON in a proton-rich nucleus changes into a neutron, releasing a positron and an electron neutrino.
Quark confinement: it is not possible to get a quark by itself as blasting a proton etc with energy just gets changed into matter - more quarks and antiquarks
1. Conservation of energy and charge: this applies to any change in science and includes rest energy of particles.
2. Conservation of baryon numbers:
3. Conservation of lepton numbers
4. Conservation of strangeness: this is conserved only in strong interactions. If it isn't conserved then it is a weak interaction.