Particle physics is a curious discipline. Its key theory, the Standard Model – our best understanding of how the basic building blocks of matter are governed by three of the four fundamental forces – is one of the most tested scientific systems and has allowed researchers to predict the existence of particles decades before we had the instruments to actually find them.
At the same time, we know that it is limited. It doesn’t include gravity for example. Or dark energy or dark matter.
These limitations are important, but they are extremely difficult to test in particle accelerators like the Large Hadron Collider (LHC). Researchers are currently approaching things in almost the opposite way by instead proving one of the many predictions of the standard model wrong. They have not had much luck with this either, but a new study inches us closer to doing just that.
As reported in the European Physical Journal C, researchers have studied a particular particle decay that happens to beauty mesons, an unstable particle made by a very rare beauty antiquark and a down quark (found in both protons and neutrons). The beauty mesons decay in a number of ways, all predicted by the standard model. However, experiments looking at these decays have detected a slight anomaly from the Standard Model predictions, suggesting either the predictions are wrong or hinting at unknown physics.
"For a long time in the LHC, there has been an intense hunt for everything whose presence cannot be explained by current physics," co-author Dr Marcin Chrzaszcz, from the Institute of Nuclear Physics and the University of Zurich, said in a statement.
"At present, the search for new particles or phenomena in a direct way remains fruitless. However, several anomalies have been found in data containing decays of beauty mesons. They are becoming more interesting day by day because the more data we process and the more effects we take into account when describing them, the better they are visible."
There was not enough data to claim a discovery but there was enough to make people raise an eyebrow about it.
To make sure that an unexpected result is not just a blip, or a fluke, or a mistake it has to be rigorously tested. If, for example, it differs from the predicted outcome by three standard deviations it has a level of 3 sigma. This anomaly had a precision of 3.4 sigma, or 99.97 percent. The goal is to confirm that the anomaly is real beyond the five sigma golden standard or 99.9999 percent.
In previous calculations, it was assumed that when the meson disintegrates, there are no more interactions between its products," co-author Dr van Dyk said.
However, when the team expanded the theoretical background of the beauty meson decay to also include long-distance interactions, according to the Standard Model, the data goes way beyond the five sigmas, up to 6.1, suggesting that there is really something there. Despite the new analysis, this is still not an official discovery but it does make the anomaly a lot more tantalizing.
"We will probably have a sufficient amount within two or three years to confirm the existence of an anomaly with a credibility entitling us to talk about a discovery," explains Dr. Chrzaszcz.
The beauty meson anomaly is the not the only experimental hint that we are close to finding physics beyond the Standard Model. We might soon have to explain a lot of phenomena, which our theoretical edifice currently cannot.