• Although the Standard Model gives a description of all of the phenomena that are known in particle physics, it is conceptually incomplete. There are a variety of indications that more fundamental physics remains to be discovered. Nevertheless, the Standard Model will describe phenomena on the scale of interactions below 100 GeV or so, and perhaps much higher. The new physics will extend and strengthen the foundations of the Standard Model, but because the Standard Model is already a relativistic quantum field theory it will remain the effective description, whether it is a fundamental theory or not. The situation is analogous to that with Maxwell's equations. They are a part of the Standard Model, but we do not think of them as wrong; they apply in their domain, but they are not the full theory.

Open Questions

• Unification into a simpler structure
  • Unification of the electroweak and QCD forces.
  • Unification of the quarks and leptons.
  Theories that include such unification are called "Grand Unified Theories".
  Unifying particle physics with gravity.
• Flavor
  • Why 3 generations ?
  • Origin of mixing parameters
  • Origin of CP violation
• Origin of Mass
  • The Higgs physics of the Standard Model has to be understood.
  • It is a part of the Standard Model, but the form of the solution may be part of transition to new physics.
    • If Higgs bosons exist as light fundamental scalars (with masses of order Mz) we will be led to one kind of world view, the kind suggested by the paths being pursued with names like supersymmetry or superstrings.
      Supersymmetry
      • a symmetry that relates fermions and bosons
    • If Higgs physics does not exist in the form of discrete particle states (one or more) a very different and presently unclear approach will be needed.
    • Whatever the outcome, at present it appears to be essentially an experimental question.