In experiments at the Paul Scherrer Institute PSI, an international research collaboration has measured the radius of the atomic nucleus of helium five times more precisely than ever before. With the ...

Helium is the second most abundant element in the Universe, after hydrogen. The nucleus of its most common isotope, helium-4, consists of two protons and two neutrons and is called the α-particle.

A new measurement of the strong nuclear force, which binds protons and neutrons together, confirms previous hints of an uncomfortable truth: We still don’t have a solid theoretical grasp of even the ...