Monday, June 13, 2022

Don't Believe The Hype

The New York Times, writing about the non-event of the Large Hadron Collider (LHC) restarting for its latest runs of experimental data gathering is big on hype and short on critical evaluation. It opens up accurately enough noting that:
The collider was shut down at the end of 2018 for extensive upgrades and repairs. According to the current schedule, the collider will run until 2025 and then shut down for two more years for other extensive upgrades to be installed.
It then talks about the discrepancy between the recent Fermilab muon g-2 measurement and one of two leading estimates of the value it should take. But, you would be hard pressed without knowing the underlying story to tell that there are two different calculations of the Standard Model of Particle Physics value of muon g-2, one at odds with experimental data and the other consistent with experimental data, from the language in bold below:
Last year, a team of some 200 physicists associated with the Fermi National Accelerator Laboratory in Illinois reported that muons spinning in a magnetic field had wobbled significantly faster than predicted by the Standard Model.

The discrepancy with theoretical predictions came in the eighth decimal place of the value of a parameter called g-2, which described how the particle responds to a magnetic field.

Scientists ascribed the fractional but real difference to the quantum whisper of as-yet-unknown particles that would materialize briefly around the muon and would affect its properties. Confirming the existence of the particles would, at last, break the Standard Model.

But two groups of theorists are still working to reconcile their predictions of what g-2 should be, while they wait for more data from the Fermilab experiment.

“The g-2 anomaly is still very much alive,” said Aida X. El-Khadra, a physicist at the University of Illinois who helped lead a three-year effort called the Muon g-2 Theory Initiative to establish a consensus prediction. “Personally, I am optimistic that the cracks in the Standard Model will add up to an earthquake. However, the exact position of the cracks may still be a moving target.”
Equally important, nobody expects the LHC that is restarting to shed any light on muon g-2 between now and the wrap up of its data collection in 2025.

The story notes the existence of hints of lepton universality violations in B meson decays in some LHC data, without noting that lepton universality violations are not seen in other decays involving the same processes, or the serious doubts cast on the statistical significant of the results due to inaccurate calculations of the expected values and failure to consider global statistical significance, discussed in papers blogged here and this blog's commentary on them.

And, the article concludes by discussing the new mass estimate for the W boson from the CDF experiment of Tevatron reached with reanalysis of old data that is starkly out of line with all of the other experimental measurements of the same quantity. Yet it doesn't even mention the widespread belief among physicists that it is the new mass measurement, and not the Standard Model, that is out of whack in this case. The LHC will provide new W boson mass measurements, and already has provided one, but the betting odds are overwhelming that the new LHC measurements will not confirm the outlier CDF measurement of this fundamental particle's mass.

The article also opens up by pronouncing that the LHC might answer questions like:
Where did the universe come from? Why is it made of matter rather than antimatter? What is the “dark matter” that suffuses the cosmos? How does the Higgs particle itself have mass?
There is no follow up in the article itself, however, to suggest any basis for these assertions. In fact, however, the LHC has almost no likelihood of answering any of those questions but the last one. And, the evidence that the last one (the source of the Higgs boson's mass) is highly likely to favor is the Standard Model answer we already have as a default answer to that question, because all data to date have closely hewed to the properties expected of a Standard Model Higgs boson predicted four decades ago.

So, don't believe the hype. 

The gray lady has declined to speak to more sober voices in the high energy physics community, but ultimately, those voices are probably going to prevail in the end, with scientific conclusions that are boring, but can give us confidence that the Standard Model works.

7 comments:

Onur Dincer said...

The gray lady has declined to speak to more sober voices in the high energy physics community, but ultimately, those voices are probably going to prevail in the end, with scientific conclusions that are boring, but can give us confidence that the Standard Model works.

The Standard Model of particle physics may well be the last word on particle physics with little, if any, modification on it in the decades and even the centuries to come. What I am more curious about is the still hotly debated area of cosmology, in particular the question of which of the cosmological models will win out. Will it be a model with a beginning of space and time (not necessarily the so-called standard model of Big Bang cosmology), a cyclic model, a multiverse model or something different, and which particular variety of those models in question? So, even if particle physics will be pretty stable and boring in the decades and even the centuries to come, there is still much room for debate, exploration and discovery in the field of cosmology and it has many indications of being far from static and boring in the coming decades at least.

andrew said...

Another paper that I recently blogged https://arxiv.org/abs/2206.05624 about experimental evidence that the universe as a whole is not isotropic or homogeneous at the very largest scales is very germane to the question of a Big Bang and after only cosmology model v. a cyclic one v. a multiverse one v. matter and antimatter counterpart mirror universes on either side of the Big Bang models, and re models of cosmological inflation.

Particle physics is important too, although less obviously, because the higher the energies at which you can experimentally prove that the SM of Particle Physics holds, and the higher the energies at which you can experimentally constrain in a somewhat model dependent way the extent to which new physics can deviate from the SM at energies above those we can directly experimentally measure based on the highest energies that we can directly measure experimentally, the shorter the time frame in which post-Big Bang energy scales that can produce big BSM effects can occur.

Basically, the higher the energies at which you can prove the SM works, the further back you can reverse engineer the history of the universe with experimentally tested physical laws, which greatly constrains the parameter space of deviations from the null hypothesis of a Big Bang with nothing that comes before it in a unique universe.

andrew said...

How do they handle matter-antimatter asymmetry?

andrew said...

The magazine "Science" offers a more sober assessment.

https://www.science.org/content/article/ten-years-after-higgs-physicists-face-nightmare-finding-nothing-else

andrew said...

I'll take a look at your references when I get a chance. They look interesting.

andrew said...

Thanks for the additional references.

Onur Dincer said...

You are welcome. I could provide more, but I do not want to burden you with more references to read.