The Fundamental Structure of the Neutron and Proton
The basic atomic structure of our Universe consists of three particles, the electron, proton and neutron, classified in physics as Fermions. The electron, as far as can be determined is fundamental, having no size that would allow for underlying structure. However, it was discovered that the neutron and proton (collectively called nucleons) were not fundamental, having a definite extension in space. This discovery hinted that there could be something hidden in the nucleons, more fundamental yet never observed, which combined to make up the physical properties of the nucleon; size, mass, charge and spin.
During the past twenty years a theory has arisen that attempts to explain the structure of baryons, such as the neutron and proton, held together by the strong force. This theory identifies quarks as the basic building blocks of the baryons.
Until 1987 the nucleon spin was thought to be a well-understood issue, with the three quarks that make up the nucleon contributing to the overall spin of the particle. However, in that year an experiment at CERN presented results that indicated that little of the proton spin is carried by the quarks.
More recent results, including an experiment at the Stanford Linear Accelerator Center, proposed by Virginia physicists, have confirmed the results of the CERN experiment. One of the most outstanding problems in particle physics is to understand the structure and origins of the spin of the nucleon. This program will permit Virginia to build the essential equipment for the next generation of experiments to help resolve this challenging question. The graduate and undergraduate students involved in this program will be doing world class basic research and this is crucial to the education of superior and enthusiastic scientists.