The mystery of the size of the proton

Researchers from the universities of Coimbra and Aveiro have contributed to deepening the mystery surrounding the size of the proton, in a study funded by FCT, now published in the journal Science.

The international team calculated that the proton has a radius of 0.84087 femtometers (or 0.000 000 000 000 000 841 meters), a value that confirms measurements made in 2010 by the same researchers, but differs from values determined by other methods. The accuracy now achieved is considerably greater, which deepens the enigma of the size of the proton. After investigating possible experimental errors, the explanation for the discrepancies between the measurements may reveal physical phenomena in the proton not yet explained by theory, or even a new physics of the interaction between subatomic particles.