LHC marches on; ten years and a lonely Higgs (Introduction)

by David Turell , Saturday, March 30, 2019, 17:59 (2043 days ago) @ David Turell

The LHC has found nothing more of significance beyond the Higgs, and it is too light according to theories. Max Strassler and his group are hunting for new findings in a different approach, but have nothing of significance to report:

https://profmattstrassler.com/2019/03/19/the-importance-and-challenges-of-open-data-at-...

No point in quotes, as they have not found anything important, so on to tehv artic le:

https://aeon.co/essays/has-the-quest-for-top-down-unification-of-physics-stalled?utm_so...

"So when the European Organization for Nuclear Research (CERN) cranked up the LHC just outside Geneva for a second time in 2015, hopes for empirical validation were running high. The fruits of physicists’ most adventurous top-down thinking would finally be put to the test. In its first three-year run, the LHC had already notched up one astounding success: in 2012, CERN announced that the Higgs boson had been found, produced in high-energy, head-on collisions between protons.

***

"This time, though, none of the more exotic particles and interactions that theorists hoped to see has been forthcoming. No ‘stop squarks’, no ‘gluinos’, no ‘neutralinos’. The null results are now encrusting the hull of the Standard Model, like barnacles on a beautiful old frigate, and dragging her down to the ocean floor. It looks like the centuries-long quest for top-down unification has stalled, and particle physics might have a full-blown crisis on its hands.

"This time, though, none of the more exotic particles and interactions that theorists hoped to see has been forthcoming. No ‘stop squarks’, no ‘gluinos’, no ‘neutralinos’. The null results are now encrusting the hull of the Standard Model, like barnacles on a beautiful old frigate, and dragging her down to the ocean floor. It looks like the centuries-long quest for top-down unification has stalled, and particle physics might have a full-blown crisis on its hands.

***

"Instead, many of us have switched from the old top-down style of working to a more humble, bottom-up approach. Instead of trying to drill down to the bedrock by coming up with a grand theory and testing it, now we’re just looking for any hints in the experimental data, and working bit by bit from there. If some measurement disagrees with the Standard Model’s predictions, we add an interacting particle with the right properties to explain it. Then we look at whether it’s consistent with all the other data. Finally, we ask how the particle and its interactions can be observed in the future, and how experiments should sieve the data in order to be able to test it.

"The bottom-up method is much less ambitious than the top-down kind, but it has two advantages: it makes fewer assumptions about theory, and it’s tightly tethered to data. This doesn’t mean we need to give up on the old unification paradigm, it just suggests that we shouldn’t be so arrogant as to think we can unify physics right now, in a single step. It means incrementalism is to be preferred to absolutism – and that we should use empirical data to check and steer us at each instance, rather than making grand claims that come crashing down when they’re finally confronted with experiment.

***

"We began with an experimental signature (the particular bottom meson decays that disagree with Standard Model predictions), then we tried to ‘bung in’ a new hypothesised particle to explain it. Its predictions must be compared with current data to check that the explanation is still viable. Then we started building an additional theoretical structure that predicted the existence of the particle, as well as its interactions. This theory will allow us to make predictions for future measurements of decays, as well as search for the direct production of the new particle at the LHC. Only after any hints from these measurements and searches have been taken into account, and the models tweaked, might we want to embed the model in a larger, more unified theoretical structure. This may drive us progressively on the unification road, rather than attempting to jump to it in one almighty leap.

Comment: Having spent so many years using the standard model, they are trying to squeeze out more info from the collider they have. Most researcher say a more powerful one is needed. But they may be disappointed again. Perhaps a new theory is needed. My quotes have skipped a get deal of theoretical considerations.