This focused the rays of a specific mass-to-charge ratio through a narrow slit. These were then detected in real time using an electrometer, doing away with the cumbersome photographic plates.

A 16-parts-per-trillion measurement of the antiproton-to-proton charge–mass ratio. Nature . Published online January 5, 2022. doi: 10.1038/s41586-021-04203-w.

Sunday Times News: The atomic mass of a specific atom or molecule is determined by using an experimental technique called mass spectrometry.

An ultrasensitive experiment comparing protons with their antimatter counterparts found no difference in the ratios of their charge to mass, researchers report in the Aug. 13 Nature.

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...