https://phys.org/news/2022-10-physicist ... roton.html
by Thomas Jefferson National Accelerator Facility
Nuclear physicists have confirmed that the current description of proton structure isn't all smooth sailing. A new precision measurement of the proton's electric polarizability performed at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility has revealed a bump in the data in probes of the proton's structure.
Though widely thought to be a fluke when seen in earlier measurements, this new, more precise measurement has confirmed the presence of the anomaly and raises questions about its origin. The research has just been published in the journal Nature.
According to Ruonan Li, first author on the new paper and a graduate student at Temple University, measurements of the proton's electric polarizability reveal how susceptible the proton is to deformation, or stretching, in an electric field. Like size or charge, the electric polarizability is a fundamental property of proton structure.
What's more, a precision determination of the proton's electric polarizability can help bridge the different descriptions of the proton. Depending on how it is probed, a proton may appear as an opaque single particle or as a composite particle made of three quarks held together by the strong force.
"We want to understand the substructure of the proton. And we can imagine it like a model with the three balanced quarks in the middle," Li explained. "Now, put the proton in the electric field. The quarks have positive or negative charges. They will move in opposite directions. So, the electric polarizability reflects how easily the proton will be distorted by the electric field."