2012 may well turn out to be The Year of The Higgs. Right now we have very little knowledge about this particle, but that may change dramatically over the year. As I described in my previous post, we’re coming toward the end of Phase 1 of the Higgs search (where the ATLAS and CMS experiments at the Large Hadron Collider [LHC] search for the simplest possible form of the Higgs particle, the Standard Model Higgs, or SM Higgs for short.) And we’re also starting up Phase 2 of the Higgs search. As discussed in my Cosmic Variance guest post, and in more detail in my most recent post, if a particle resembling the SM Higgs is found, Phase 2 involves checking its details and determining as well as possible whether it is or isn’t precisely what is predicted by the Standard Model. If no such particle is found, Phase 2 involves searching widely for the many other types of Higgs particles that nature might or might not possess. Fortunately, despite these apparently divergent aims, the two possible branches of Phase 2 involve asking some of the same experimental questions (see Figure 3 of the most recent post), and so we can start on Phase 2 before even finishing Phase 1. And that is happening now.
One of the things that has to be done in Phase 2 is to search for decays of the Higgs particle that are not among the decays predicted to occur in the Standard Model. [“Decay” = “a disintegration of one particle into two or more”. Click here for an introduction.] Such “exotic” decays are thought of as particularly plausible, because a lightweight Higgs (below about 150 GeV/c2 or so) is a very sensitive creature. It is very easy for new particles and/or forces to alter the Higgs’ properties, perhaps causing changes in how (or how often) it is produced, and to what (and with what probability) it may decay. As shown in a large number of papers, written by quite a variety of particle physics theorists, there are many, many types of possible exotic decays, and they can arise for many reasons. If you’re curious what kind of exotic decays might occur, I gave a few examples in my now somewhat out-of-date analysis of what the summer’s Higgs searches imply. The basic logic of how unusual Higgs decays might arise is still correct in the cases described, but there are many, many more possibilities too. I’ll have to write a long article about the options in the coming month or so.