Particle physics experiments

Experiments show ‘something fundamental’ may be wrong in understanding ‘quantum scum of the universe’

This undated photo provided by Fermi National Accelerator Laboratory in April 2022 shows the facility’s collider detector outside Batavia, Illinois. In results released Thursday, lab scientists calculated that the W boson, a fundamental particle in physics, weighs a little more than their theoretical rulebook for the universe tells them it should. (Fermilab via AP)

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CHICAGO — The Grand Explanation physicists use to describe how the universe works may have major new flaws to fix after a fundamental particle turns out to have more mass than scientists thought.

“It’s not just something wrong,” said Dave Toback, a particle physicist at Texas A&M University and spokesman for the US government’s Fermi National Accelerator Lab, which conducted the experiments. If replicated by other labs, “it literally means that something fundamental in our understanding of nature is wrong.”

Physicists in the lab smashed particles together for 10 years and measured the mass of 4 million W bosons. These subatomic particles are responsible for a fundamental force at the center of atoms, and they only exist for a fraction of a second. before disintegrating into other particles.

“They constantly appear and disappear in the quantum foam of the universe,” Toback said.

The difference in mass from what the prevailing theory of the universe predicts is too big to be a rounding error or anything that could be easily explained, according to the study by a team of 400 scientists from the worldwide published Thursday in the journal Science.

The result is so extraordinary that it needs to be confirmed by another experiment, say the scientists. If confirmed, it would present one of the biggest problems yet with scientists’ detailed rulebook for the cosmos, called the Standard Model.

Duke University physicist Ashutosh V. Kotwal, the project leader for the analysis, said it’s like finding out there’s a hidden room in your house.

Scientists have speculated that there might be an undiscovered particle that interacts with the W boson that could explain the difference. Perhaps dark matter, another poorly understood component of the universe, could play a role. Or maybe there’s just new physics involved that they just don’t understand at the moment, the researchers said.

The standard model says that a W boson should measure 80,357,000 electron volts, plus or minus six.

“We found a little more than that. Not that much, but it’s enough,” said Giorgio Chiarelli, another Fermi team scientist and research director at Italy’s National Institute of Nuclear Physics. The Fermi team scale put the W boson at 80,433,000 electron volts heavier, plus or minus nine.


Quantum mechanics is really beautiful and weird. Anyone who hasn’t been deeply troubled by quantum mechanics hasn’t understood it.

–Dave Toback, particle physicist at Texas A&M University


It doesn’t seem like a big difference, but it is a huge one in the subatomic world.

But the team and experts not involved in the research said such a claim requires further evidence from a second team, which they do not yet have.

“It’s an incredibly tricky measurement, it requires understanding various calibrations of various small effects,” said Claudio Campagnari, a particle physicist at the University of California, Santa Barbara, who was not part of the Fermi team. . “These guys are really good. And I take them very seriously. But I think ultimately what we need is confirmation from another experience.”

Earlier, less precise measurements of the W boson by other teams found it to be lighter than expected, so “maybe there’s just something weird about this experiment,” the physicist said. Caltech Sean M. Carroll, who was not part of the research and said it was “absolutely worth taking very seriously.”

The discovery is significant because of its potential effect on the Standard Model of physics.

“Nature has facts,” Duke’s Kotwal said. “The model is how we understand these facts.”

Scientists have long known that the Standard Model is not perfect. It doesn’t explain dark matter or gravity well. If scientists have to go in and tinker to explain these findings, they need to make sure it doesn’t mess up the mathematical equations that now explain and predict many other particles and forces, the researchers said.

This is a recurring problem with the model. A year ago, another team discovered another problem with the Standard Model and the reaction of muons.

“Quantum mechanics is really beautiful and weird,” Toback said. “Anyone who hasn’t been deeply troubled by quantum mechanics hasn’t understood it.”

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