A Newly Measured Particle Could Break Known Physics

Physicists have found a small discrepancy in the weight of the W boson, which could signal a huge shift in fundamental physics.

The measurement, reported in the journal Science, came from a vintage particle collider that smashed its final protons a decade ago. The roughly 400 members of the CDF collaboration have continued to analyze W bosons produced by the collider, chasing down numerous sources of error to reach an unparalleled level of precision.

If the excess heft can be independently confirmed, it would imply the existence of undiscovered particles or forces, which would bring about the first major rewrite of the laws of quantum physics in half a century.

This would be a complete change in how we see the world and it could even be as important as the 2012 discovery of the Higgs boson. This would be a completely new area.

The physics community is hungry for flaws in the standard model of particle physics, the long-reigning set of equations capturing all known particles and forces. The nature of dark matter is one of the grand mysteries left unanswered by the standard model. A credible threat to the standard model is made by the CDF collaboration's strong track record.

Aida El-Khadra is a theoretical physicist at the University of Illinois.

There is no champagne yet. The new W mass measurement is different from the standard model, but other experiments weighing the W have produced less dramatic results. The W particle's mass was measured by the ATLAS experiment at Europe's Large Hadron collider and found to be only a hair heavier than what the standard model says. One or both groups overlooked some subtle quirk of their experiments according to the clash between CDF and ATLAS.

Guillaume Unal is a physicist at the Large Hadron collider and a member of the ATLAS experiment.

It's a monumental piece of work, but it's very hard, said Frank Wilczek, a physicist who won a Nobel Prize.

Weak dogs.

The weak force is one of the four fundamental forces. The weak force does not push or pull so much as it transforms heavier particles into lighter ones. A muon spontaneously decays into a W boson and a neutrino, for instance, and the W becomes an electron and another neutrino. The sun shines because of the subatomic shape-changing that causes radioactivity.

Over the last 40 years, various experiments have measured the W and Z bosons. The mass of the W boson has proved to be an attractive target. The W mass can be predicted by combining several measurable quantum properties in the standard model equations.