The model of particle physics at the dawn of a revolution?

New work brings us closer to the fifth fundamental force in physics, whose existence became clearer last March.

Last March, CERN’s LHC, a particle accelerator, threw a storm in the scientific community by announcing the probable discovery of a fifth fundamental force in physics. Recently, physicists at the University of Cambridge made new discoveries that seem to confirm these initial results.

Physics today is formalized in what is called the Standard Model of particle physics. He is the one who describes how our world works at the smallest scale. According to Harry Cliff, particle physicist at Cambridge and lead author of this new study, it is “the most successful scientific theory ever built ”… Even if we know full well that it has pitfalls.

For example, she completely forgets one of the four fundamental forces that we know today. It perfectly describes the electromagnetic force, the weak interaction, and the strong interaction, but on the other hand it leaves the gravitational interaction aside. Nor is it sufficient to explain certain obscure phenomena such as dark matter.

A missing piece of the puzzle

Physicists have therefore suspected for a long time that some ingredients must be missing in the recipe they are proposing. As Harry Cliff explains in his article, to find this missing ingredient, physicists quickly turned to one of the six fundamental particles: bottom quarks (or beauty quarks in English).

These quarks are the embodiment of instability; they exist for an infinitesimal fraction of a second before transforming into a collection of other particles. Cliff explains that to identify the missing actors, it is interesting to study the details of this transformation.

This is where the initial discovery of last March came from. According to the Standard Model, the bottom quarks should have produced two other particles – electrons and muons – at the same frequency. However, they found that the latter appear slightly less often. A most interesting observation; this indeed suggests that a new strength, not included in the standard model, would be the origin of this imbalance.

But these were only preliminary results. The big concern is that the initial data was not precise, or rather not enough. Because in a discipline as demanding as particle physics, the usual statistical thresholds are no longer sufficient. For a phenomenon to be considered established, much stricter criteria of precision must be applied; we are talking about a standard deviation at 5 sigma. Without going into detail, this means that we are trying to ensure that there is less than a one in a million chance that this observation is insignificant. It is therefore an excellent safety threshold; if it is achieved, we can consider that a result is extremely solid.

Getting closer and closer to the goal

It is therefore necessary to deepen these results to get closer to these famous 5 sigma. This is what the Harry Cliff team has been looking to do since last March. And for that, there is only one solution: to dive back into the data. They therefore looked for other traces of this peculiarity of the disintegration process. By analyzing the interaction of the bottom quarters with another type of particle – the up quarks – they have indeed observed the same phenomenon as their colleagues last March.

“We could be on the verge of a major discovery. ” -Harry Cliff

Unfortunately, again, their results still show a margin of error of 2%. A score still far from the famous 5 sigma. On the other hand, it seems to indicate that all these beautiful people are actually on the right track. “Our results are very close to those of previous work, and further strengthen the idea that we could be on the verge of a major discovery.”, Explains Harry Cliff.

To get their hands on indisputable proof once and for all, however, physicists will have to wait until their favorite toy is operational. Indeed, the LHCb is currently in a construction phase; eventually, it should be able to produce collisions at a much higher frequency. This will allow us to get more statistical data on this phenomenon, and, perhaps, to finally get our hands on one of the missing parts of the standard model.

The text of this new study is available here.

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