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Full Version: How the LHC may spell the end of particle physics
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http://backreaction.blogspot.com/2018/12...ticle.html

INTRO (Sabine Hossenfelder): The Large Hadron Collider (LHC) recently completed its second experimental run. It now undergoes a scheduled upgrade to somewhat higher energies, at which more data will be collected. Besides the Higgs-boson, the LHC has not found any new elementary particle.

It is possible that in the data yet to come some new particle eventually shows up. But particle physicists are nervous. It’s not looking good – besides a few anomalies that are not statistically significant, there is no evidence for anything out of the normal. And if the LHC finds nothing new, there is no reason to think the next larger collider will. In which case, why build one?

That the LHC finds the Higgs and nothing else was dubbed the “nightmare scenario” for a reason. For 30 years, particle physicists have told us that the LHC should find something besides that, something exciting: a particle for dark matter, additional dimensions of space, or maybe a new type of symmetry. Something that would prove that the standard model is not all there is. But this didn’t happen.

All those predictions for new physics were based on arguments from naturalness. I explained in my book that naturalness arguments are not mathematically sound and one shouldn’t have trusted them.

The problem particle physicists now have is that naturalness was the only reason to think that there should be new physics at the LHC. That’s why they are getting nervous. Without naturalness, there is no argument for new physics at energies even higher than that of the LHC. (Not until 15 orders of magnitude higher, which is when the quantum structure of spacetime should become noticeable. But energies so large will remain inaccessible for the foreseeable future.)

How have particle physicists reacted to the situation? Largely by pretending nothing happened.

One half continues to hope that something will show up in the data, eventually. Maybe naturalness is just more complicated than we thought. The other half pre-emptively fabricates arguments for why a next larger collider should see new particles. And a few just haven’t noticed they walked past the edge of the cliff. A recent report about Beyond the Standard Model Physics at the LHC, for example, still iterates that “naturalness [is] the main motivation to expect new physics.”

Regardless of their coping strategy, a lot of particle physicists probably now wish they had never made those predictions. Therefore I think it’s a great time to look at who said what. References below....

MORE (details): http://backreaction.blogspot.com/2018/12...ticle.html
What a colossal waste of money. I was never hopeful that increasingly larger colliders would produce anything much in the way of final, definitive answers.