Key Terms
Virtual particle
A particle that cannot be directly observed but whose effects can be observed.
Given
Range of strong nuclear force ~ 1 fermi = 1e-15 m.
Result
Predicted pion mass ~ 200 MeV/c^2.
Quantum electrodynamics (QED)
The quantum mechanics of electromagnetism; governs electromagnetic interactions at the submicroscopic scale. Spectacular
Problem with stationary target
Momentum must be conserved, so recoil takes energy; limits fraction of beam energy available for particle creation.
Antimatter trick
Create the antimatter counterpart of the beam particle (opposite charge); it circulates in the opposite direction in the
Formula
Total energy = number of gaps times voltage per gap. Example: 800-MeV protons, 2000 accelerating tubes: V per gap = 800
WWII
Accelerators built; "particle zoo" of hundreds of particles discovered.
When particle meets antiparticle
Annihilation. Mass converts entirely to energy — typically photons.
Hadrons
Feel the strong nuclear force. Also feel weak.
Boson
Integer intrinsic spin (0, 1, 2...). Does NOT obey Pauli exclusion principle.
Fermion
Half-integer intrinsic spin (1/2, 3/2...). Obeys Pauli exclusion principle.
Gauge bosons
The carrier particles (photon, W+, W-, Z0, gluons, graviton).
Assignment
+1 for the particle, -1 for its antiparticle, 0 for everything else.
Solution
Assign a new quantum number called strangeness (S).