Science: W boson shakes up particle physics


The Standard Model of particle physics cannot explain some of the features of the W-boson, the fundamental particle of matter.

Image of CERN in Geneva.


One of the fundamental particles of matter, the W boson, will have more mass than theory predicts, shaking the house of cards of the Standard Model of particle physics, according to a study published Thursday in the journal Science. .

“There are hints that some parts are missing from the Standard Model, and we are bringing in a new, very interesting and very important part,” its lead author, Professor Ashutosh Koutal, a physicist at Duke American University, told AFP.

Basis of radioactivity

This theory explains all the measurements made in the field of elementary particle physics, that is, the infinitely small world, the elements of which make up atoms and the forces that control them. The standard model, refined in the second half of the twentieth century.and century, allows you to “make fantastically accurate predictions” about the behavior of these particles, explains physicist Harry Cliff of the University of Cambridge.

Like the W-boson, a particle that transmits, in particular, the so-called weak interaction between other particles of matter. It is the basis of radioactivity and, beyond that, nuclear fusion reactions like those that power the sun. All these particles and forces are connected in a kind of equilibrium. For example, the mass of the W boson is limited by the mass of the Higgs boson.

“Extraordinary Affirmations”

“The Standard Model predicts equilibrium, and the experimental result presented to us contradicts this prediction,” physicist and CNRS research director Jan Stark told AFP. This “house of cards” is crumbling after the announcement of a study that the mass of the W boson is larger than expected. A collaborative feat of the CDF, a group of approximately 400 scientists led by P.R Koutal was to measure this mass of 80,433 mega-electronvolts with unprecedented accuracy (0.01%), twice the best available.

This is the result of a decade of analysis of a sample of 4 million particles produced at the Tevatron, a particle accelerator at Fermilab in the US, which is now closed. This accelerator, like the LHC at CERN in Europe (which made it possible to identify the Higgs boson), causes particles to collide with each other at phenomenal speed, exposing their constituent elements, destroying them.

Now another team, on a different instrument, must confirm the results of this study to prove it. Because, as Ian Stark reminds us, “extraordinary claims require extraordinary evidence.”

“Animated Discussions”

A serious problem, given the extreme accuracy of the measurement, which cannot be a matter of statistical chance. Thus, “this is either a major discovery or a problem in data analysis,” comments Jan Stark, who predicts “quite lively discussions in the coming years.”

The CDF collaboration announcement is the latest in a series of “cracks that have been appearing for several years in the Standard Model, with precise measurements contradicting the model’s predictions,” the physicists and authors of another article in Science note. If confirmed, this discovery could betray the existence of “new interactions or new particles” that today’s experiments are not yet able to reveal.

“Big in Infinitely Big”

If physicists are looking for head lice in this way, it’s because the Standard Model, in particular, struggles to explain “the great thing about infinitely big,” dark matter, according to Ian Stark, who runs the aptly named Lab. . des 2 infinis (L2IT) at the Paul Sabatier University in Toulouse.

Some observations, such as the speed of galaxies in galaxy clusters or the anomalous rotation speed of some stars, have led astrophysicists to theorize that there is a hypothetical “dark matter” that enlivens these phenomena. But nothing in the Standard Model explains what kind of particles this “dark matter” consists of. “We follow the path without neglecting any trace. That’s why we eventually understand”, wants to believe PR Kotval.


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