Baryon form factors ((03) S01)

• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2012 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 204404729

Besides electron scattering experiments, information on baryon structure can also be obtained from atomic spectroscopy. Surprisingly, the extraction of the proton charge radius from muonic hydrogen Lamb shift is in strong contradiction, by around 5.6 standard deviations, with the values obtained from energy level shifts in electronic hydrogen or from electron-proton scattering. This "proton radius puzzle" has triggered a large activity worldwide. This project combines experimental and theoretical efforts to advance the precision frontier on baryon form factors. The experimental program will study nucleon spacelike form factors at MAMI, as well as their timelike counterparts at BESIII in Beijing. The theoretical counterpart uses dispersive, effective field theory and lattice methods.

• DFG Programme: Collaborative Research Centres
• Subproject of: SFB 1044: The Low-Energy Frontier of the Standard Model: From Quarks and Gluons to Hadrons and Nuclei
• Applicant Institution: Johannes Gutenberg-Universität Mainz
• Co-Applicant Institution: GSI Helmholtzzentrum für Schwerionenforschung GmbH; Helmholtz-Institut Mainz
• Project Heads: Professor Dr. Frank Maas; Dr. Harald Merkel; Professor Harvey Byron Meyer, Ph.D.; Professor Dr. Marc Vanderhaeghen