Classification Of Particles

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There are many different types of particle apart from your usual ones. They only appear in cosmic rays and in particle accelerators, they decay very quicklyso they're difficult to get a handle on.


  • Hadrons are particles that feel the strong nulear force (or strong nuclear interaction).
  • Eg, protons are positive so they need at strong force to hold them together.
  • Hadrons are not fundamental particles, they are made up of smaller particles called quarks (see quark notes).
  • Hadrons can be subdivided into two groups: baryons and mesons. They are lassified by the number of quarks they contain.


  • Protons and neutons are baryons.
  • All baryons are unstable apart from the proton. This means they decay to become different particles.
  • The particle they end up as depends on what the baryon was before it decayed, but it ALWAYS include as proton.
  • Some theories predict that protons should decay with a VERY long half-life but there is no evidence for it at the moment. 
  • Antiprotons and antineutrons are antibayrons.
  • you don't find antibayons in ordinary matter.

Baryon Number

  • The number of bayons in an interaction is called the baryon number.
  • Baryons (protons and neutrons) have a baryon number of +1.
  • Antibaryons (antiprotons and antineutrons) have a baryon number of -1.
  • Other baryons are given…


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