HADRONS

HADRONS

1. Hadrons are particles that feel the STRONG NULEAR FORCE

2. Baryons

   • 3 quark particles - nucleons
     • Proton - uud
       • Only stable baryon - all baryons decay into protons
       • Decay into neutrons by β+ decay
     • Antineutron
     • Neutron - udd
       • Decay into protons by β− decay
     • Antiproton

3. Mesons

   • Quark -antiquark pairs
     • Pions (π )
       • π 0
         • up, anti up
         • down, anti down
         • strange, anti strange
       • π -
         • down, anti up
       • π +
         • up, anti down
       • Discovered in cosmic rays
       • High energy particle collisions
     • Kaons (K)
       • K+
         • up, anti strange
       • K0
         • down, anti strange
         • strange, anti down
       • Kaons (K-mesons) are heavier and more unstable than pions.
       • K-
         • strange, anti up

4. All quarks decay by WEAK FORCE

5. Quarks & Antiquarks

   • Up
     • Charge: +2/3
   • Down
     • Charge: -1/3
   • Strange
     • Charge: -1/3
   • Anti-Up
     • Charge: -2/3
   • Anti-Down
     • Charge: +1/3
   • Anti-Strange
     • Charge: +1/3

6. Mesons interact with baryons via the strong force

7. Properties conserved in particle interactions

   • Charge
   • Baryon number
   • Strangeness
   • Lepton number
     • 3 generations of lepton have to be conserved separately

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