A Higgs or not a Higgs? What to do if you discover a new scalar particle

We show how to systematically analyze what may be inferred should a new scalar particle be discovered in collider experiments. Our approach is systematic in the sense that we perform the analysis in a manner which minimizes a priori theoretical assumptions as to the nature of the scalar particle. For instance, we do not immediately make the common assumption that a new scalar particle is a Higgs boson, and so must interact with a strength proportional to the mass of the particles with which it couples. We show how to compare different observables, and so to develop a decision tree from which the nature of the new particle may be discerned. We define several categories of models, which summarize the kinds of distinctions which the first experiments can make.