Physicists have found that an elementary particle known as the W boson appears to be 0.1% too heavy – a small difference that could herald a major change in fundamental physics.
Measure, April 7 report in the magazine Science, which comes from a classical particle collider at the Fermi National Accelerator Laboratory in Batavia, Illinois, that smashed its last protons a decade ago. Some 400 members of the Collision Detector at Fermilab (CDF) collaboration have continued to analyze the W bosons produced by the collider, known as the Tevatron, eliminating a multitude of error sources to achieve the degree unmatched precision.
If the excess weight of W over standard theoretical predictions could be independently confirmed, this finding would imply the existence of unexplored particles or forces and would bring about a rewrite. the first major of the laws of quantum physics in half a century.
“This is going to be a complete change in the way we see the world,” even potentially rivaling the 2012 discovery of the Higgs boson in meaning, said. Sven Heinemeyer, a physicist at the Institute for Theoretical Physics in Madrid, who is not part of the CDF. “The Higgs boson fits well with the previously known picture. This will be a brand new area that will be included. “
The discovery comes at a time when the physics community is hungry for flaws in the standard model of particle physics, a long-standing set of equations that capture all known particles and forces. The standard model is known to be incomplete, leaving many great mysteries unsolved, such as the nature of dark matter. The strong track record of the CDF collaboration makes their new results a credible threat to the standard model.
“They made hundreds of beautiful measurements,” says Aida El Khadra, a theoretical physicist at the University of Illinois, Urbana-Champaign. “They are known to be careful.”
But no one has opened the champagne yet. While the new mass W measurement, taken alone, is quite different from the predictions of the standard model, other experiments measuring the mass W have produced less dramatic (albeit less accurate) results. than). In 2017for example, testing ATLAS at Europe’s Large Hadron Collider measure the mass of the particle W and found it was only a hair heavier than what the standard model said. The conflict between CDF and ATLAS suggests that one or both groups have overlooked some of their sophisticated experiments.
“I wanted to confirm it and understand the difference from previous measurements,” said Guillaume Unal, a physicist at CERN, the laboratory that owns the Large Hadron Collider and a member of the ATLAS experiment. . “The W boson must be the same on both sides of the Atlantic.”
“It was a monumental work,” said Frank Wilczeka physicist who won a Nobel Prize at the Massachusetts Institute of Technology, “but it was difficult to know what to do with it.”
Weak Bosons
The W bosons, along with the Z bosons, mediate the weak force, one of the four fundamental forces of the universe. Unlike gravity, electromagnetism, and the strong force, the weak force doesn’t push or pull as much as it turns heavier particles into lighter ones. For example, a muon spontaneously decays to a W boson and a neutrino, and W then becomes an electron and another neutrino. The related subatomic conformational change causes radioactivity and helps the sun shine.
Various kinds of experiments have been measuring the masses of the W and Z bosons for the past 40 years. The mass of the W boson has proven to be a particularly attractive target. While other particle masses must simply be measured and accepted as facts of nature, the mass W can be predicted by incorporating a handful of other measurable quantum properties in standard model equations.
