1. Fundamental Particles
Atomic Physics
Fundamental Particles

2. Fundamental Particles
Background history: The discovery of antimatter in cosmic radiation supported the theory developed from the special theory of relativity and quantum theory that all fundamental particles have a corresponding antimatter particle.

3. Hadrons and Leptons
The original antimatter particles discovered were antiproton, antineutron, and antielectron. But during more modern experiments more particles were discovered in the cosmic radiation. All these new particles were placed into two groups Hadrons – those particles affected by the strong force Leptons – those not affected by the strong force

4. Hadrons
Hadrons are made up of smaller particles themselves called quarks.
Quarks come in “flavors”
Up (u)
Down (d)
Strange (s)
The quarks have charge and strangeness, and antiquarks are opposite

5. Protons and Neutrons are made of three quarks
*In strong interactions, the quark flavor is conserved*

6. Leptons Leptons are not affected by the strong force.
Electrons, neutrinos, antimatter partners, positron, antineutrino etc.…
Not composed of smaller particles, are considered fundamental particles
Quark flavor is not conserved during beta radioactive decay
This led to the discovery of another force, the weak force.

7. Leptons
The total lepton number before a reaction is equal to the total lepton number after the reaction. But flavor is not conserved. Example decay:

8. Example
State the values of charge and strangeness for the antiquarks of up and down.

9. Example A up quark changed to a down quark
Describe the reaction where a proton in the nucleus turns into a neutron and emits a beta particle in terms of the quark model.
A up quark changed to a down quark