Going nowhere fast: Is particle physics in crisis?

Is particle physics in crisis?

This super-massive Higgs boson is meant to be the result of quantum fluctuations: an ultra-heavy particle-antiparticle pair, produced for a fleeting instant and then subsequently annihilated. Quantum fluctuations of ultra-heavy particle pairs should have a profound effect on the Higgs boson, whose mass is very sensitive to them. The other particles in the Standard Model are shielded from such quantum effects by certain mathematical symmetries – that is, things don’t change under transformation, like a square turned through 90 degrees – but the Higgs boson is the odd one out, and feels the influence very keenly.

Except that it doesn’t, because the mass of the Higgs appears to be so small. One logical option is that nature has chosen the initial value of the Higgs boson mass to precisely offset these quantum fluctuations, to an accuracy of one in 1016. However, that possibility seems remote at best, because the initial value and the quantum fluctuation have nothing to do with each other. It would be akin to dropping a sharp pencil onto a table and having it land exactly upright, balanced on its point. In physics terms, the configuration of the pencil is unnatural or fine-tuned. Just as the movement of air or tiny vibrations should make the pencil fall over, the mass of the Higgs shouldn’t be so perfectly calibrated that it has the ability to cancel out quantum fluctuations.
However, instead of an uncanny correspondence, maybe the naturalness problem with the Higgs boson could be explained away by a new, more foundational theory: supersymmetry.

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The trouble is that it’s not clear when to give up on supersymmetry. True, as more data arrives from the LHC with no sign of superpartners, the heavier they would have to be if they existed, and the less they solve the problem. But there’s no obvious point at which one says ‘ah well, that’s it – now supersymmetry is dead’. Everyone has their own biased point in time at which they stop believing, at least enough to stop working on it. The LHC is still going and there’s still plenty of effort going into the search for superpartners, but many of my colleagues have moved on to new research topics. For the first 20 years of my scientific career, I cut my teeth on figuring out ways to detect the presence of superpartners in LHC data. Now I’ve all but dropped it as a research topic. 

It could be that we got the wrong end of the stick with how we frame the puzzle of the Higgs boson. Perhaps we’re missing something from the mathematical framework with which we calculate its mass. Researchers have worked along these lines and so far come up with nothing, but that doesn’t mean there’s no solution. Another suspicion relates to the fact that the hypothesis of heavy particles relies on arguments based on a quantum theory of gravity – and such a theory has not yet been verified, although there are mathematically consistent constructions.
Perhaps the bleakest sign of a flaw in present approaches to particle physics is that the naturalness problem isn’t confined to the Higgs boson. Calculations tell us that the energy of empty space (inferred from cosmological measurements to be tiny) should be huge. This would make the outer reaches of the universe decelerate away from us, when in fact observations of certain distant supernovae suggest that the outer reaches of our universe are accelerating. Supersymmetry doesn’t fix this conflict. Many of us began to suspect that whatever solved this more difficult issue with the universe’s vacuum energy would solve the other, milder one concerning the mass of the Higgs.

[url=https://aeon.co/essays/has-the-quest-for-top-down-unification-of-physics-stalled]