Higher-Order QED for Precision Electromagnetic Probes of Hadronic Structure

George Washington University, Washington DC

Investigators

Abstract

Crucial information about the properties of atomic nuclei, the main building blocks of matter, is obtained from scattering of electron beams accelerated to energies of billions of electron-volts. Electron accelerators such as the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) are capable of recreating three-dimensional images of not only an atomic nucleus, but also of its elementary constituents - quarks - and their interactions. Such high resolution imaging is needed to obtain key information about the still undiscovered physics guiding formation of nuclear structure. However, the high resolution of electron probes can be obscured by the fact that electromagnetic effects described by quantum electrodynamics (QED) are only about a factor of a hundred times weaker than the strong interactions within atomic nuclei. In this context, this project will make possible precision corrections for electromagnetic effects into a self-consistent analysis of electron scattering by nucleons and nuclei. In addition, the PI will mentor students engaged in this state-of-the-art scientific research in nuclear theory. This projects will allow the development of the theoretical framework needed to include higher-order electromagnetic effects into analysis of key physics processes of charged lepton scattering to be studied experimentally at Jefferson Lab and a future Electron-Ion Collider. The effects of higher-order QED corrections for electron-proton and electron-nucleus scattering will be examined in detail. In particular, the PI and his collaborators will analyze multi-photon and radiation corrections for elastic and inelastic electron scattering on a nucleon and nuclei. Particular nuclear reactions and effects to be considered are: (a) Deep exclusive processes on a nucleon: Effects due to two-photon exchange. (b) QED loop effects for T-odd asymmetries of semi-inclusive deep-inelastic electron-nucleon scattering (SIDIS). (c) Coulomb effects in single-spin asymmetries of electron scattering from nuclei. (d) Lepton mass effects for two-photon corrections in elastic scattering of electrons and muons on a proton. The PI will develop a user-friendly web interface that will allow researchers in this field to run calculations that will improve the accuracy of electron (and muon) scattering studies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.