The old "proton radius puzzle" which was an unanswered problem about the size of the proton has been solved by Mississippi State University scientists. The research is called "Proton Radius Experiment" and three of the national scientific team who performed the research were MSU physicists. The research is published today in Nature.
The MSU faculty members participated in the research were Physics Professors Dipgankar Dutta, James A. Dunne, and Assistant Professor Lamiaa El-Fassi.
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According to Dutta, the research confirms that proton is slightly smaller than it was thought before. He said "our results show there is no discrepancy in proton size when measured using ordinary hydrogen atoms or an exotic form of hydrogen atoms."
The size or charge radius of a proton has always been an important quantity in physics. For many years, the charge radius of the proton had been obtained from high precision measurement of the energy levels of the hydrogen atom or by scattering electrons from hydrogen atoms.
"Given the precision of the measurements, the muonic hydrogen and regular hydrogen results being this different, just by chance, was less than about 1 in a 100 billion. This was called the ‘proton charge radius puzzle’ and led to a rush of experimental as well as theoretical efforts to understand why the size of the proton appears to be different when measured in regular hydrogen versus muonic hydrogen," said Dutta in the research. "The results of the PRad experiment effectively seem to resolve the ‘proton radius puzzle,’ and close the door on the possibility that the ‘puzzle’ was an indication of the existence of a new fifth force in nature."
The research was the conclusion of a larger collaboration led by MSU and Duke, Idaho State and North Carolina A&T State universities.