A very heavy particle disrupts physics

Mathilde Fontes, Editor-in-Chief of the Scientific Journal EpsilonToday, he evokes a discovery announced a few days ago that caused a huge noise in the field of physics.

franceinfo: OHe measured n the mass of the particle, which is very high, which may mean that the theories of matter should be rewritten?

Mathilde Fontes: Yes, the value of mass measured in the past and, more importantly, predicted by theory was about 80,357 MeV. The mass that has just been published by the collaboration of nearly 400 physicists is 80443.5. So, we agree, the difference is not huge: only 0.09%. But these measurements are accurate: this difference is enough to say there’s a problem, and that there’s something we didn’t understand.

Is it a part of the substance that has been measured?

that it An elementary particle called a W boson : a particle of the same family as the photon, a particle of light. Except that the W boson does not transmit electromagnetism, it does transmit a nuclear force: it is involved in radioactivity. It was discovered in 1983, and has been studied a lot since then, in the particle collider, these large tunnels in which particles are pushed at the speed of light, so that they explode against each other, giving rise to secondary particles that can be studied. .

It’s data of this kind that speaks volumes today: data from the Tevatron, an American collider that operated between 1984 and 2011. It took physicists 10 years to process it, extract the corresponding signal for millions of W bosons, and find their mass.

So the W boson is too heavy?

Yes a little heavy. So we can tell ourselves that we were simply wrong about this mass, and that it doesn’t change much. Except that in the theory of matter – this theory is called the Standard Model – all properties of particles are described, and they are related to each other. If we are wrong about the mass of the W boson, then this means that the theory is wrong and that it has a problem. This is great news!

Why the good news?

Because physicists know the Standard Model is incomplete. They have been searching for decades for clues that could lead them to complete it. In particular, this theory fails to describe gravity—we don’t know how to describe, on a microscopic scale, the force that makes apples fall from trees, and that keeps our feet on the ground. So it is a great hope that opens today thanks to W BosonTo find the breach to unravel this mystery.