Claims of the Imminent Death of Particle Physics are Greatly Exaggerated
June 4, 2007
On the strength of totally unverified rumors (propagated by yours truly), Slate tells us that particle physicists are all hoping that the Higgs hasn’t been found at DØ, because otherwise the LHC would have been built for nothing:
That’s why particle physicists, and the EU member states that have spent Nepal’s annual GDP to build this accelerator, are hoping that no one, in Chicago or Switzerland, finds the Higgs. The future of high-energy physics lies with the small chance that the standard model is wrong, and something exotic happens at LHC energies.
Partial credit. In a sense the future of HEP as an experimental science does depend on the Standard Model being wrong. If nothing other than a SM Higgs appears at the TeV energy scale, it will be very difficult to answer the outstanding issues of the model (such as the famous “naturalness” problem of why the Higgs mass would be so low compared to the natural scale of gravity).
However: if the rumors are proven true, then the Standard Model is wrong (and wrong in a deep way, too, unlike the hacks used to add neutrino masses). I can’t say this strongly enough: THE SUPPOSED DØ PARTICLE CAN NOT BE THE STANDARD MODEL HIGGS. The cross section (the rate at which the particles are made) is much too high. All the theoretial interpretations I’ve heard invoke supersymmetry — in particular the so-called Minimal Supersymmetric Standard Model (MSSM) — to increase the production rate for their Higgs equivalent enough that DØ could have detected it. To explain the fact that DØ sees a signal at all, you need non-Standard Model physics.
The Higgs and the MSSM are not incompatible. In fact, in one of its particle-multiplying feats, the MSSM demands five physical Higgs bosons (generally, for each particle we know of, it gives you one or two new ones to look for). Discovering the MSSM, while a little conventional (in the sense that the scenario’s implications have been pored over by lots of theorists for a couple of decades now), would be the opposite of a disaster for particle physics, and the LHC would have a lot to do. It’s actually quite difficult to get rid of the Higgs in reasonable models of any kind, so the mere existence of a Higgs-type particle doesn’t tell you much; you have to look at any candidate carefully to distinguish between models.
Bottom line: If the DØ signal is real, it’s physics beyond the Standard Model. If so, it’s extremely likely that additional phenomena will be revealed by the LHC, and we will get our money’s worth.