I was about to leave a comment there, but since I am a very discontinuous blog reader (you either write or read, in this business -no time for both things together) I feared I would then miss any reply or ensuing discussion. Not that I mean to say anything controversial or flippant; on the contrary, I mostly agree with Adam's assessment of the situation. With some distinguos.
He observes that it is by now a plain fact that there is nothing to be seen at LHC energies, and he correctly describes the situation as a bunch of people going their own independent way through the five stages of grief, and most of them past the denial phase. But then he writes:
On the experimental side we will inevitably see, just for economical reasons, less focus on high-energy colliders and more on smaller experiments.
I think I disagree with this. Economical reasons are a factor, but the effort toward a larger-than-LHC machine is quite significant as seen from my end:
1 - The LHC itself will still be around (it will also still be round) for two more decades at least, with the high-luminosity project already approved and funded; and the prospects of upgrading it by increasing the power of its magnets, to reach into 30 TeV, are concrete.
2 - The interest toward a linear collider is worldwide, and the motivation for such a machine is maybe not overwhelming but quite solid: we have a new particle, and we need to study it in detail, so let's produce it in e+e- collisions.
3 - China is a new big player in the game of building huge machines, and a new big collider there does not look like a fairy tale anymore. What for (in scientific terms), that's another question.
I believe Adam correctly observes that there's an increasing interest toward "sideways" to investigate the problems facing HEP at the moment. He mentions precision physics as the way to look forward, as loop effects in precision observables can ultimately tell us what lies beyond. I would add that there is still enough left to learn about non-perturbative QCD to feed a new generation of particle physicist for many decades. While it is true that the new "exotic" resonances we observe in the few GeV mass range (e.g. the X,Y,Z states studied by LHCb and others) are not exotic per se, they still are a manifestation of physics we don't really know how to describe properly.
In a concluding paragraph, Adam puts down a few interesting questions:
All in all, there are good reasons to worry, but also tons of new data in store and lots of fascinating questions to answer. Will the B-meson anomalies pan out? What shall we do after we hit the neutrino floor? Will the 21cm observations allow us to understand what dark matter is? Will China build a 100 TeV collider? Or maybe a radio telescope on the Moon instead? Are experimentalists still needed now that we have machine learning? How will physics change with the centre of gravity moving to Asia?
I will allow myself to answer a few of these with one-liners:
Will the B-meson anomalies pan out ? Of course they will, one way or the other... Which one, that is the question.
What to do after we hit the neutrino floor ? It's easy: we will keep digging ! (The neutrino floor is the rate at which direct dark matter experiments expect to observe interactions from neutrinos, which makes the searches much harder although not impossible).
Are experimentalists still needed now that we have ML ? I would say yes, as without experimentalists there are no data to analyze. But I could turn this into the same question for theorist model-builders - that job can nowadays be taken by machines too!
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Tommaso Dorigo is an experimental particle physicist who works for the INFN at the University of Padova, and collaborates with the CMS experiment at the CERN LHC. He coordinates the European network AMVA4NewPhysics as well as research in accelerator-based physics for INFN-Padova, and is an editor of the journal Reviews in Physics. In 2016 Dorigo published the book “Anomaly! Collider physics and the quest for new phenomena at Fermilab”. You can get a copy of the book on Amazon.
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