Laser-powered hydrogen experiment resolves long-running proton size mystery

Colorado State University physicists measured the proton radius in hydrogen at about 0.84 femtometers using ultraviolet lasers and a two-laser-field method.

The result was independently confirmed by the Max Planck Institute and agrees with newer measurements and Standard Model predictions.

This helps resolve the long-running proton radius puzzle caused by conflicting electron- and muon-based experiments.

The finding strengthens confidence in the Standard Model and reduces the likelihood that new particle physics is needed to explain the discrepancy.