Scientists Baffled As Particle Experiment Threatens 'Fundamental' Theory

Scientists have made a particle physics discovery that they say could mean nothing less than the upheaval of our entire model of the building blocks of the universe—if their results can be independently replicated.

The finding relates to a fundamental particle called the W boson which was first discovered in 1983. Together with another particle called the Z boson it is responsible for the weak force, one of the four fundamental forces that matter in the universe experiences, together with the strong force, electromagnetism and gravity.

The weak force is essentially what allows protons to turn into neutrons and vice-versa, and without it nuclear fusion—the process that powers stars—would not be possible.

Scientists have been trying to calculate how much the W boson weighs, and they've done this by studying 4 million of them produced by the Tevatron particle collider at the Fermi National Accelerator Laboratory in Illinois in experiments that ran from 2002 to 2011.

LHC museum display
A visitor looks at a display dedicated to the Large Hadron Collider at the Science Museum in London in November, 2013. Scientists have used the Tevatron particle collider at the Fermi National Accelerator Laboratory in Illinois to study fundamental particles called W bosons. Peter Macdiarmid/Getty

The Standard Model of particle physics predicts that the W boson should have a mass of around 80,357 million electron volts (MeV). However, according to the Tevatron accelerator data, the measurement came out to about 80,433.5 MeV.

This might not seem like much of a difference at first, but it could have some serious implications for the Standard Model. It's a difference seven times larger than the margin of error would allow for.

According to Harry Cliff, a particle physicist at the University of Cambridge in the U.K., there are three main possible explanations for the difference in the numbers. One is that the Tevatron scientists made a mistake; another is that the Standard Model's prediction contains a mistake; and the other is that both are right, in which case it would mean something very important has happened.

"If we can eliminate the first two possibilities, then the only remaining explanation for the W boson being heavier than predicted is the unseen influence of new particles that we haven't discovered yet, which could open a door to a whole new subatomic world and help us solve some of the big outstanding problems in fundamental physics," Cliff told Newsweek.

"However, extraordinary claims require extraordinary evidence and before we get to that point we need to be able to exclude the possibility of a mistake in the measurement.

"So in short, it's certainly very interesting but physicists should keep the champagne on ice for now."

The next step is for the scientists to collaborate with others using different particle accelerators around the world, including the Large Hadron Collider at CERN in Switzerland, to see if the results can be replicated.

If they can, "it literally means something fundamental in our understanding of nature is wrong," said Dave Toback, a particle physicist at Texas A&M University and a spokesperson for the Fermi National Accelerator Laboratory, which conducted the experiments.

The W boson research was published in the journal Science on April 7 and involved around 400 different scientists.