Princeton Univ., PCTS Visiting Lectureship Series 2014

The discovery of a light Higgs boson completes the Standard Model of particle physics and suggests a definite agent for the symmetry breaking that the model requires. However, the Standard Model has always seemed incomplete. The reality of the light Higgs boson tells us that we must take the conceptual gaps in this model much more seriously. One popular solution to the issues raised by the Standard Model is the assumption of supersymmetry at the TeV energy scale. This solution is still in play, but it is increasingly constrained by negative results of searches at the Large Hadron Collider. It is thus important to note that there is a very different approach to the questions of the Standard Model based on the idea that the Higgs boson is the relic of new strong interactions at the 10 TeV energy scale. In these models, the Higgs boson is a pseudo- Goldstone boson or has some other, similarly cogent, reason to be a light scalar particle. In these lectures, I will review the structure of these "Composite Higgs" models and discuss the properties of the most important new ingredients. I will also discuss the question of "naturalness" in these models and the related question of where the new particles that they predict should be found.