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There are four forces in nature: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. And each of them is associated with a particle, or quantum, that carries the minimum unit of each force. Thus, the carrier particle of electromagnetism is the photon, that of the strong nuclear force is the gluon, which holds the quarks that form protons and neutrons tightly together inside the atomic nuclei, and the W and Z bosons are the carriers. of the weak force, responsible for the radioactive decay of subatomic particles. Only gravity, for the moment, escapes this rule, since no one has yet managed to find a ‘graviton‘.
Now, after a long decade of meticulous tests and measurements, a team of physicists led by Ashutosh Kotwalof Duke University, has just announced that the mass of W bosonwhich governs the weak nuclear force, is “significantly larger” than the theories predict.
Something that could shake the foundations of our understanding of the Universe and affect the Standard Model of particle physics, the best theory that scientists have to describe the basic components of matter and the forces that govern them. The finding has just been published in ‘Science’.
As Kotwal himself explains, this result, the most precise measurement of the W boson to date, was obtained by a group of more than 400 scientists, who for a decade examined up to four million W bosons in “a data set of around 450 trillion collisions”, carried out at the Tevatron collider in Illinois, the largest in the world until 2009, when that ‘title’ passed to large hadron collider CERN, at CERN (Geneva). The Tevatron stopped operating in 2011, but physicists have been processing its data ever since.
According to the study, the researchers managed to determine the mass of the W boson with an accuracy of 0.01 percent. Which, they explain, is equivalent to calculating the weight of a 350-kilogram gorilla with a margin of error of 40 grams. In this way, they discovered that the mass of the boson is notably higher than that predicted by the Standard Model. “And if this is real,” explains Harry Clifffrom the University of Cambridge – and not systematic bias or misunderstanding about how to do the calculations, then it’s a big deal because it would mean there’s a fundamental new ingredient for our universe that we hadn’t discovered before.”
The Standard Model it is undoubtedly one of the most successful theories out there, capable of making remarkably accurate predictions, but it is not without its problems. For example, it says nothing about dark matter, which together with ‘dark energy’ accounts for no more and no less than 95% of the mass of the Universe. And neither does it explain why we live in a Universe made of matter, when it is assumed, according to theory, that the same amount of matter and antimatter was created during the Big Bang.
“In this framework of clues that parts are missing from the Standard Model -says Kotval- we have provided one more clue. And it’s about something big.” Now, according to the researchers, “it’s up to the theoretical physics community and other experiments to follow up on this and shed light on this mystery.” Kotwal himself assures that, after a whole decade of effort, his work is not yet finished. “We follow the clues -says the physicist- and we will leave no stone unturned, so we will find out what this means.”
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