12 July 2012
The standard model of particle physics assumes the Higgs boson is an elementary particle. But what if, rather like the proton, it is itself made up of particles?
We know the standard model is incomplete because it cannot explain all the phenomena we observe (see “Beyond Higgs: Deviant decays hint at exotic physics”). Tweaking the model to make the Higgs a composite of quark-like particles, bound together by a new force, could solve this problem. It turns out that there is more than one way to arrange these new particles and forces to produce something akin to dark matter.
To see if the boson reported last week at CERN near Geneva, Switzerland, could be such a composite, Alex Pomarol from the Autonomous University of Barcelona in Spain has started to compare decay data for the new particle with predictions of how a composite Higgs would decay inside the Large Hadron Collider. He told the International Conference on High Energy Physics in Melbourne, Australia, that the observed decays are not outside the range predicted by composite models – and that a composite Higgs is a possibility.
The idea is not new, and “it’s not so crazy because we’ve seen it all before with the proton”, says Tony Gherghetta, a theoretical physicist at the University of Melbourne. Although the proton was discovered near the beginning of the 20th century, it wasn’t until the 1970s that physicists realised, “oh wait a minute, the proton is not an elementary particle, it’s actually made up of other constituents”, he says. These constituents are now known to be quarks and gluons.