E08-007: Measurement of the Proton Elastic Form Factor Ratio at Low Q2
Experiment E08-007 is part of a series of investigations of the structure of the proton. These investigations involve measurements of the proton's form factors, which represent the proton's response to being probed by electron scattering as a function of energy. Measuring the form factors provides information on the actual distribution of electric charge and current (magnetization) inside the proton.
By making extremely precise comparisons of the proton's charge and magnetization, scientists can look for small differences between the two distributions, indicating the effect of the motion of the proton's building blocks: quarks. In addition, this experiment will measure the form factors at low energies, which is sensitive to the large-scale distribution of the quarks. This allows scientists to test the picture of the proton as a small-sized core of quarks surrounded by a larger "cloud" of particles called pions.
While this experiment is similar to Hall C's E04-108, the two experiments have different goals. E04-108 is designed to push the limit of how deeply scientists can peer into the proton by going to very high energy, while E08-007 aims to greatly enhance the precision with which the proton's form factors can be measured at lower energies.