Research in Theoretical Hadronic Physics and Related Topics

College Of William And Mary, Williamsburg VA

Investigators

Abstract

This theoretical project will support current searches for physics beyond the Standard Model of particle physics. Although the Standard Model has been successful in describing the elementary particles that make up most of known matter in the Universe, many questions still remain unanswered. The theoretical calculations by the investigator and his collaborators will support and suggest new avenues for low-energy experiments sensitive for signatures of new physics. A prominent such example is the proton radius puzzle, where measuring the proton radius using electrons gives different results than using muons. The PI will calculate corrections needed for the interpretation of the data and will study beyond the Standard Model hypotheses to explain the proton radius puzzle, along with suggesting new experiments for future testing of these ideas. Another example is the case of precision electron-proton scattering experiments with polarized electrons, where the PI will do calculations relevant to extensions of the initial experiments that may allow measuring properties of short-lived excited states of the proton and the possibility of comparing them to predictions based on the current theoretical understanding of the physics involved. Postdoctoral fellows and undergraduates will be trained and supported by this project. One thrust of the project is to find corrections to the energy levels of muonic helium and deuterium due to the polarization of the nuclear cores by the near-by orbiting muons. Precise results are needed to evaluate the measured energy level data and interpret it in terms of radius discrepancies relative to corresponding measurements using electrons. Another thrust is to calculate two photon corrections to polarized electron scattering in the region where the Delta resonance, one of the short-lived proton excitations, exists. To study the Delta as an entity in itself, one produces it using one photon and then measures it almost immediately by a further scattering with a second photon. In this project, the PI will calculate the precision requirements needed to obtain reliably the size and magnetic parameters of the Delta meson.