Particles

6.4.2 Particles

All particles have an anti-particle, which have the same mass but opposite charge (if charged!).

To show anti-particles we draw a bar on top of the symbol:

6.4.2-1 Classification of particles

6.4.2-2 Hadrons

All hadrons are made of quarks:

Quarks			Anti-quarks
Name	symbol	charge	Name	Symbol	charge
up			Anti-up
Down			Anti-down
strange			Anti-strange

Quark combinations of Baryons:

Charge of a proton = +1 à uud =

Charge of a neutron = 0 à udd =

Quark combination of mesons:

6.4.2-3 Leptons

Leptons are not made of anything. We call them fundamental or elementary particles.

You already know electrons, or  ; and its anti-particle: positron:

Neutrino does not have charge, extremely small mass, almost zero!

Two types that you should know: 

• Electron neutrino:
• Electron anti-neutrino:

Beta-minus () decay

A neutron in the nucleus decays into a proton. Then an electron and an Electron anti-neutrino are ejected:

Charge on both sides of an interaction should be equal (conservation of charge!).

Looking at it from quarks transformation perspective.

Which can be written only with the changing quarks:

If you check the charge for individual quarks, that should be conserved as well!

Beta-plus () decay

A proton inside the nucleus decays into a neutron. Then a positron, and electron neutrino are ejected.

Four fundamental forces

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