A new high-precision measurement of the mass of an elementary particle can shake the structures of the so-called standard model, a theoretical framework that explains how all known particles in nature act and interact. Or not.
The result, published in the latest issue of the journal Science, concerns the mass of the W boson, one of the particles carrying the weak nuclear force, linked to certain processes of radioactive decay. It was obtained by the international collaboration CDF (Collider Detector at Fermilab), based on analyzes of a decade of data from the Tevatron accelerator, which operated until 2011. According to the group, the new measurement is approximately twice as accurate as the best efforts. previous. And it shows a much heavier W boson than expected. Much more, in particle physics, is 0.1%.
It may seem like a small change and even easy to accommodate. After all, of the three forces that the standard model successfully contemplates – the electromagnetic, carried by the photon, the particle that light is made of; the strong nuclear force, carried by the gluon, responsible for the agglutination of protons and neutrons and for the stability of atomic nuclei; and the weak nuclear force, of the Z and W bosons, of the decays –, the latter seems to have a very restricted action. But that’s not how the band plays.
The Standard Model, while flexible (for example, fitting a small mass for neutrinos that were previously assumed to be massless), is a bit like a house of cards, and the W particle, with the weak nuclear force, is close to the base. Its properties fit the theory with other observable parameters, such as the charge of the electron and the mass of other particles. That is, if the mass of the W is very different, some ingredient begins to be missing to keep everything else that has already been exhaustively measured in its proper place.
Of course, this is a potential discrepancy that many physicists are eager to find. After all, as complete as it is, we know that in fact there are missing pieces in this great theoretical framework – apart from gravity, described by general relativity and which refuses to speak the idiom of quantum mechanics (the lingua franca of the standard model), it still needs to be explained. what are the mysterious dark matter and energy.
However, it cannot be ignored that the standard model has been working like a clock for decades, anticipating discoveries and becoming the most successful in the history of physics. The more established a theory, the higher the bar an experiment must jump to shake it. And it plays against the new result the fact that two previous measurements, although apparently less accurate, matched pretty well with the standard model – and are incompatible with the novelty. That is, we will need future measurements, even more precise (perhaps coming from the LHC), to see if there is really new physics coming out there.
This column is published on Mondays, in Folha Corrida.
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