Particle Physics

Elementary particles have no internal structure ... they are not made out of smaller constituents

Proton and Neutron are composite particles. Electron still believed to be elementary

Quarks, Leptons, and Exchange particles (charts pg 720). Quarks and Leptons are associated with matter. Exchange particles refer to interactions or forces.

Quantum numbers are properties used to characterize particles ... like electric charge and flavor.

Antiparticles. To every particle there corresponds an antiparticle of the same mass as the particle but of opposite electric charge. Yet they may have other quantum numbers that are different.

Spin, short for spin angular momentum. This is more of a term than a definition in the classical sense. Elementary particles may be point particles and it is not possible for a point to spin around its own axis.

Unit of spin = (h/2pi), h = Planck's constant

Bosons (photons and mesons) have integral spin and Fermions (quarks, leptons, protons and neutrons) have half-integral spin.

The spin value dictates the possible orientations of spin. (i.e. 1/2 spin is two orientations. 1 spin is three. 3/2 spin is four, etc.)

Pauli exclusion principle. It is impossible for two identical fermions (half integral spin) to occupy the same quantum state if they have the same quantum numbers. So no two fermions can have the same set of quantum numbers. This is why only two electrons (a fermion) can occupy the inner most shell. One will have up spin and the other down spin. The outer layers also have angular momentum since electrons are orbiting the nucleus and so can be distinguished from different values of their angular momentum, so more than two electrons can occupy the outer shells.

HW. PG 729: 1, 2, 3. and take the particle adventure tour working through "what is fundamental?" and "what is the world made of?"


CERN: Standard Model

The Particle Adventure ... Imperative that you take this tour through the history of particle physics.

Elegant Universe reading.
Charts of elementary particles

Sixty Symbols ... quarks, four forces, neutrinos, Feynman diagrams, electrons.


Mass of a Proton ... Empty Space