The death of supersymmetry

The Economist mag reported:

“The great tragedy of science”, said Thomas Huxley, “is the slaying of a beautiful hypothesis by an ugly fact.” That, though, is the scientific method. If nature provides clear evidence that a hypothesis is wrong then you have to abandon it or at least modify it. It is psychologically uncomfortable, no doubt, for those with an interest in the correctness of the hypothesis in question. But at least everybody knows where they stand.

What happens, though, in the opposite case: when nature fails to contradict a hypothesis but stubbornly refuses to provide any facts that support it? Then nobody knows where he stands. This is fast becoming the case for a crucial hypothesis in physics, called Supersymmetry — or Susy, to its friends. Susy attempts to tie up many of the loose ends in physical theory by providing each of the known fundamental particles of matter and energy with a “supersymmetric” partner particle, called a sparticle. It is neat. It is elegant. But it is still unsupported by any actual facts. And 2017 looks like the year when the theory will either be confirmed or dropped.

No, it was not neat or elegant.

Theorists liked it because it could be used to cancel certain anomalies. With SUSY, string theory only need 6 extra dimensions instead of 22.

The Standard Model is neat and elegant because it models the universe with only about 20 parameters. Supersymmetric models all require at least 120 extra parameters, none of which have any connection to any known observational reality.

The SUSY models thus forced a vast and unnecessary complexity. Ptolemaic epicycles made much more sense, as they were only introduced to the extent needed to explain observations.

Sabine Hossenfelder posted that naturalness is nonsense. One could believe in supersymmetry independent of naturalness, but the two concepts seem to have the same followers. They have an almost religious belief that the universe will conform to their peculiar notions of beauty. For an example of such a believer, see Lubos Motl.