An unexpected boson measurement threatens the standard model of physics

After a decade of painstaking measurements, scientists announced Thursday that a fundamental particle – the W boson – has a significantly larger mass than theoretically assumed, which shakes the foundations of our understanding of how the universe works.

These fundamentals are grounded by the standard model particle physics, which is the best theory scientists have to describe the most basic building blocks of the universe and what forces control them.

The W boson governs the so-called weak force, one of the four basic forces of nature and thus a pillar of the standard model.

However, new research Published in science said that the most accurate measurement ever made of the W boson directly contradicts the model’s prediction.

Ashutosh Kotwal, a Duke University physicist who led the study, told AFP that it took more than 400 scientists more than 10 years to identify four million W boson candidates from a “data set of roughly 450 trillion collisions.” investigate.

These collisions – caused by smashing particles together at breathtaking speeds to study them – were carried out by the Tevatron accelerator in the US state of Illinois.

It was the world’s most energetic particle accelerator until it was replaced by the in 2009 Large Hadron Collider near Geneva, which is known to have observed the Higgs boson a few years later.

The Tevatron stopped running in 2011, but scientists at Fermilab’s Collider Detector (CDF) have been cracking numbers ever since.

A diagram showing the fundamental particles of the Standard Model. (Science Alert)

“Cracks” in the model

Harry Cliff, a particle physicist at Cambridge University who works at the Large Hadron Collider, said the Standard Model is “probably the most successful scientific theory ever written down”.

“It can make fantastically accurate predictions,” he said. But if these predictions turn out to be wrong, the model cannot simply be optimized.

“It’s like a house of cards, if you pull it a little too hard, the whole thing collapses,” Cliff told AFP.

The standard model is not without problems.

For example, it is not taken into account Dark matterthe together with dark energy is said to make up 95 percent of the universe. It also says that the universe should not have existed at all because the Big Bang should have destroyed itself.

In addition, “a few cracks have recently been exposed” in the model, physicists said in a companion note science Article.

“In this framework of clues that parts of the Standard Model are missing, we contributed another clue that is very interesting and quite large,” Kotwal said.

Jan Stark, physicist and research director at France’s CNRS institute, said: “This is either a big discovery or a problem in data analysis” and predicted “rather heated discussions in the coming years”.

He told AFP that “extraordinary claims require extraordinary evidence.”

‘Big Deal’

The CDF scientists said they had determined the mass of the W boson with an accuracy of 0.01 percent – double that of previous efforts.

They compared it to measuring the weight of a 350-kilogram (800-pound) gorilla at 40 grams (1.5 ounces).

They found that the boson differs from the Standard Model’s prediction by seven standard deviations, also known as sigma.

Cliff said that if you toss a coin, “the chance of getting a five sigma result through stupid luck is one in three and a half million”.

“If this is real and not a systematic bias or a misunderstanding in making the calculations, then it’s a big deal because it would mean that there is a new fundamental component of our universe that we have not discovered before.” he said.

“But if you want to say something that big, like we’ve broken the Standard Model of particle physics and there are new particles to discover, you probably need more than one measurement from more than one experiment to convince people.”

David Toback, co-spokesperson for the CDF, said that “it is now up to the theoretical physics community and other experiments to follow this up and shed light on this mystery.”

And after a decade of measurements, Kotwal isn’t done yet.

“We’ll follow the clues and leave no stone unturned, so we’ll find out what that means.”

© Media Agency France

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