Eric A. Hessels is a

Canadian Canadians () are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of their being ''C ...

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

, currently a

Canada Research Chair Canada Research Chair (CRC) is a title given to certain Canadian university research professors by the Canada Research Chairs Program. Program goals The Canada Research Chair program was established in 2000 as a part of the Government of Canada ...

and Distinguished

Research Professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a 'person who professes'. Professors ...

York University York University (), also known as YorkU or simply YU), is a public university, public research university in Toronto, Ontario, Canada. It is Canada's third-largest university, and it has approximately 53,500 students, 7,000 faculty and staff, ...

in Toronto, Ontario. In September 2019, Hessels et al. measured the

Lamb shift In physics, the Lamb shift, named after Willis Lamb, is an anomalous difference in energy between two electron orbitals in a hydrogen atom. The difference was not predicted by theory and it cannot be derived from the Dirac equation, which pre ...

for

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

to measure the radius of a

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

and demonstrated that it is consistent with the value obtained for muonic hydrogen. This proved that the supposed discrepancy known as the proton radius puzzle did not exist.

References

Year of birth missing (living people) Living people Academic staff of York University Canadian physicists 21st-century Canadian astronomers University of Notre Dame alumni Canada Research Chairs {{physicist-stub