Electroweak Symmetry Breaking
The problems of the breakdown of electroweak and flavor symmetries are among the most pressing facing particle physics today. Electroweak symmetry breaking is manifested by the nonzero masses of the weak W and Z bosons, and requires the existence of a Higgs boson or some other yet unseen mechanism. To solve the problem of flavor, one must understand why there are six quarks and six leptons forming three families, and why these particles exhibit such a peculiar pattern of masses and mixing. This question has become especially acute with the recent experimental proof that neutrinos have mass and experience oscillations. Several theoretical approaches to electroweak and flavor symmetry breaking, as well as the related question of CP violation, are being investigated actively. All of them require that there be new particles and new interactions at soon-to-be accessible energies. In particular, experiments at the Large Hadron Collider are currently accumulating data which should clarify the origins of electroweak symmetry breaking. The high-energy theorists are interacting closely with their experimental colleagues who will be working on these experiments. Research is aimed at formulating consistent theoretical models and exploring their observable consequences.