Sunday, August 28, 2011

Supersymmetry on the spot

The UK BBC reports:
Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics.

Researchers failed to find evidence of so-called "supersymmetric" particles, which many physicists had hoped would plug holes in the current theory. ...

According to Dr Tara Shears of Liverpool University, a spokesman for the LHCb experiment: "It does rather put supersymmetry on the spot".
That is some sort of British jargon for saying that supersymmetry theory has failed.
Dr Joseph Lykken of Fermilab, who is among the conference organisers, says he and others working in the field are "disappointed" by the results - or rather, the lack of them.

"There's a certain amount of worry that's creeping into our discussions," he told BBC News.

The worry is that the basic idea of supersymmetry might be wrong.

"It's a beautiful idea. It explains dark matter, it explains the Higgs boson, it explains some aspects of cosmology; but that doesn't mean it's right.

"It could be that this whole framework has some fundamental flaws and we have to start over again and figure out a new direction," he said. ...

And the new generation has the backing of an old hand - Professor George Smoot, Nobel prizewinner for his work on the cosmic microwave background and one of the world's most respected physicists.

"Supersymmetry is an extremely beautiful model," he said.

"It's got symmetry, it's super and it's been taught in Europe for decades as the correct model because it is so beautiful; but there's no experimental data to say that it is correct."
This is a repeat of what the NY Times reported in 2006, with more data to back it up. I listed the ten main arguments for supersymmetric string theory here.

Supersymmetry theory conjectures that every known particle, such as an electron and photon, is paired with an evil twin, that the evil twin has completely different properties such as mass and magnetic spin, and that at high energies there is a symmetry between a particle and its evil twin that causes a miraculous cancelation. All this supposed makes the fundamental forces more unifiedd. The trouble is that all those evil twin particles have never been seen, and there is no evidence for that unification anyway.

Lubos Motl comments:
The possibility that the LHC may discover nothing new besides the Standard Model (including one Higgs boson) is not a shocking new revelation: it's been discussed as one of the most likely scenarios for more than a decade. It has usually been presented as the ultimate nightmare scenario or as the death of particle physics.

I have always found such emotional descriptions loaded. The purpose of science is to understand how Nature works;
Yes, but it was $10B to find out that nature works the same way that it was believed to work 30 years ago. It is the most expensive null experiment ever.

Update: Peter Woit points to a 1993 NY Times article titled, 315 Physicists Report Failure In Search for Supersymmetry.


  1. Are you saying that the Standard Model is the best we have so the LHC was always likely to be a waste of money? The thought has crossed my mind.

    Maybe we tend to over-invest in good theories, harming our ability to find even better ones.

  2. It would be great if they found the Higgs or the dark matter particle. But a lot of theoretical physicists are heavily invested in exotic theories like supersymmetry, and they seem very unlikely to me.