Quarks & Leptons

Quarks & Leptons

1. Collisions

   • Leptons and anti-leptons can interact to produce hadrons

2. Neutrinos

   • Travel almost as fast as the speed of light
   • Come from space
   • Can be produced in smaller numbers when particles in accelerators collide
   • Discovered by switching the reactor on and off, which affected an experiment only explained by neutrino flow from the reactor
   • Neutrinos produced in beta decays are different from those produced in muon decays.
     • Those from muon decays create only muons, no electrons when they interact with protons and neutrons
     • So muon neutrino and electron neutrino

3. Rules

   • Leptons can change into other leptons through the weak interaction and can be produced or annihilated in particle-antiparticle interactions
   • Don't break down into non leptons
     • Fundamental
   • In an interaction between a lepton and a hadron, a neutrino or antineutrino can change into of from a corresponding charged lepton
   • Lepton number must be conserved
     • Lepton - +1
     • Anti-lepton - -1
     • Non-lepton - 0
   • Can't be applied to all
     • Electron branch sonsists of electrons, electron neutrinos and their antiparticles
     • The nuon branch consisting of muons, muon neutrinos and their antiparticles
     • Leptons are in 2 branches, the electron branch and the muon branch
     • The lepton number for each branch is conserved in any change

4. Strangeness

   • K mesons
     • Decay into pions only, or into pions and protons
   • Although they all decay through the weak interaction
     • Those that decay into pions only were referred to as K mesons
     • The others, such as the sigma, were found to
       • Have different rest masses which were always greater than that of the proton
       • Decay either in sequence or directly into protons and pions
   • Introduced to explain why certain reactions weren't observed