PSI press releasesLamb Shift Experiment

An international team of scientists confirmed the surprisingly small value of the proton radius with laser spectroscopy of exotic hydrogen. The experiments were carried out at PSI which is the only research institute in the world providing the necessary amount of muons for the production of the exotic hydrogen atoms made up of a muon and a proton.

The proton à one of the smallest building-blocks of all matter à is even smaller than had previously been assumed. This discovery is the result of experiments carried out at the Paul Scherrer Institute (PSI) in Villigen, Switzerland, by an international research team.