Paris (AFP)- After a decade of meticulous measurements, scientists announced on Thursday that a fundamental particle – the W boson – has a mass significantly greater than theoretical, shaking the foundations of our understanding of how the universe works.
These foundations are based on the Standard Model of particle physics, which is the best theory available to scientists for describing the most basic building blocks of the universe and the forces that govern them.
The W boson governs what is called the weak force, one of the four fundamental forces of nature, and therefore a pillar of the standard model.
However, new research published in the journal Science indicates that the most accurate measurement of the W boson ever made directly contradicts the model’s prediction.
Ashutosh Kotwal, a Duke University physicist who led the study, told AFP the result took more than 400 scientists over 10 years to examine four million candidate W bosons on a “dataset of ‘about 450 trillion collisions’.
These collisions – made by smashing particles together at mind-blowing speeds to study them – were made by the Tevatron collider in the US state of Illinois.
It was the highest-energy particle accelerator in the world until 2009, when it was supplanted by the Large Hadron Collider near Geneva, which observed the Higgs boson a few years later.
The Tevatron stopped working in 2011, but scientists at Fermilab’s Collider Detector (CDF) have been calculating ever since.
‘Cracks’ in the model
Harry Cliff, a particle physicist at the University of Cambridge who works at the Large Hadron Collider, said the Standard Model is “probably the most successful scientific theory that has ever been written”.
“He can make incredibly accurate predictions,” he said. But if these predictions turn out to be wrong, the model cannot simply be changed.
“It’s like a house of cards, we draw a little too much, everything collapses,” Cliff told AFP.
The standard model is not without its problems.
For example, it ignores dark matter, which together with dark energy would make up 95% of the universe. He also says that the universe shouldn’t have existed in the first place, because the Big Bang should have wiped out.
In addition to that, “a few cracks have recently been exposed” in the model, the physicists said in a companion Science article.
“Within this framework of clues that the standard model is missing parts, we have provided an additional clue, which is very interesting and quite important,” Kotwal said.
Jan Stark, physicist and research director at the CNRS, declared “that it is either a major discovery or a problem in the analysis of the data”, predicting “quite heated discussions in the years to to come”.
He told AFP that “extraordinary allegations require extraordinary evidence”.
CDF scientists said they determined the mass of the W boson with an accuracy of 0.01%, twice as accurate as previous efforts.
They compared it to a gorilla’s weight measurement of 350 kilograms (800 pounds) at less than 40 grams (1.5 ounces).
They found that the boson differed from the Standard Model prediction by seven standard deviations, also known as sigma.
Cliff said that if you tossed a coin, “the odds of getting a five sigma result by stupid luck are one in three and a half million”.
“If this is real, and not a systematic bias or a misunderstanding of how to do the math, then that’s a big deal because it would mean there’s a fundamental new ingredient in our universe that we don’t have. discovered before,” he said.
“But if you’re going to say something as important as we’ve broken the standard model of particle physics, and there are new particles to be discovered, to convince people of that, you probably need more ‘a measure of more than one experience.’
CDF co-spokesman David Toback said “it’s now up to the theoretical physics community and other experiments to follow this and shed some light on this mystery.”
And after a decade of measures, Kotwal is not done yet.
“We’re following the clues and leaving no stone unturned, so we’ll figure out what that means.”
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