The proton represents the electrically charged subatomic particle of the nucleus of an atom. In the 1990s, the size of a proton was estimated at 0.88 femtometer. However, new research has revealed that the proton would be probably smaller compared to old estimates. Indeed, a new study has shown that the interpretation of old measurements is erroneous.
This discovery surprised the scientific community and some researchers even suggested that it could modify the standard model of particle physics. Thanks to a new method, scientists were able to analyze the results of old and new experiments in more detail than before.
Specifically, these physicists found that the radius of a proton is 0.84 femtometres. This study was conducted by several physicists from the University of Bonn and the Technical University of Darmstadt.
Towards a modification of the current model?
The elastic scattering is a method for determining the radius of a proton. Indeed, it consists in bombarding a beam of electrons on a proton in an accelerator. When electrons collide with protons, the two change direction. The larger the proton, the more frequent these collisions are, which makes it possible to have a precise measurement the size of the protons.
According to Ulf Meissner, professor at the Helmholtz Institute for Radiological and Nuclear Physics at the University of Bonn, the high speed of the electron beam also makes it possible to obtain a more exact measurement. Therefore, the determination of the size of a proton would be possible thanks to the events and the type of the elastic scattering.
“We have developed a theoretical basis for using these events to calculate the radius of the proton. This allows us to take into account data that was so far left out. »
Hans-Werner Hamer, professor at the Technical University of Darmstadt
Towards a deeper understanding of particle physics
Based on the events of the scattering, these researchers reanalyzed earlier and recent experimental data, including the previously announced value of 0.88 femtometer. With the new information obtained, they were able to obtain a 0.84 femtometer radius. This corresponds to the radius determined by current measurements with a totally different method.
Furthermore, this method also improves the understanding of the fine structure of uncharged protons and neutrons.