Hadrons (AQA A Level Physics)

Baryons & Mesons

Hadrons

• Hadrons are the group of subatomic particles that are made up of quarks

• Therefore, hadrons can feel the strong nuclear force

• There are two classes of hadrons:

  • Baryons (3 quarks)

  • Mesons (quark and anti–quark pair)

• The most common baryons are protons and neutrons

• The most common mesons are pions and kaons

Hadrons may be either a baryon or a meson

Anti–hadrons

• There are two classes of anti–hadrons:

  • Anti–baryons (3 anti-quarks)

  • Anti–mesons (quark and anti–quark pair)

Anti-hadrons may be either an anti-baryon or an anti-meson

• Quarks have never been discovered on their own, always in pairs or groups of three

• Note that all baryons or mesons have integer (whole number) charges eg. +1e, -2e etc.

• This means quarks in a baryon are either all quarks or all anti–quarks. Combination of quarks and anti–quarks don’t exist in a baryon

  • e.g.

    

• The anti–particle of a meson is still a quark and anti–quark pair. The difference being the quark becomes the anti–quark and vice versa