John Arrington joined the Medium Energy Physics group in 1998 and is interested in understanding the quark/gluon structure of matter. His experiments utilize scattering of relatively high energy particles from protons, neutrons and nuclei to study their internal structure.
Electron scattering measurements from the proton and neutron provide information on the spatial structure and momentum distributions of their quarks, including information on the difference between "up" and "down" quarks and the elusive role of heavier "strange" quarks. He also works on measurements using positron and muon scattering to better map out the proton’s internal landscape and to try and understand the "proton radius puzzle" – a difference between electron and muon based measurements of the proton’s size.
John’s work on nuclei addresses the long standing question of whether the internal structure of protons is changed within the dense environment of a nucleus. His measurements focus on probing small, high-density clusters of protons and neutrons. In addition to representing extremely dense and energetic configurations within nuclei, such clusters may be the best place to isolate the impact of the nuclear environment on the internal structure of protons and neutrons.