Fundamental Particles Atomic Physics Fundamental Particles

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.

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

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

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

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.

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:

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

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