Puzzling problem: Karsten Schuhmann (left) and Aldo Antognini of the Paul Scherrer Institute inspect the laser system that was used for the laser spectroscopy measurements on muonic deuterium.

Physicists get closer to solving the proton radius puzzle with unique new measurement of the charge radius of the proton Textbook pictures make atomic nuclei seem tidy, but they are actually fuzzy ...

A discrepancy in the measured size of the “deuteron” increases the chance that something is amiss in our understanding of atoms. The same group that discovered a curious discrepancy in measurements of ...

A new measurement method suggests that the proton, a crucial subatomic particle in the Universe, is smaller than previously believed. All visible matter in the ...