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Abstract：
The proton electric charge radius (rp) is not only an important quantity as it characterizes the spatial distribution of the proton's charge, but also an essential physical input for the bound-state Quantum Electrodynamics calculations for the hydrogen atomic energy levels. Moreover, it is highly correlated with the Rydberg constant in atomic spectroscopy. In 2010, an unprecedentedly precise rp result was obtained using a novel muonic hydrogen spectroscopy technique (replacing the electron of a hydrogen atom with a muon). Nevertheless, this result triggered the “proton charge radius puzzle”, as it was 7σ smaller than measurements from previous ep elastic scattering and ordinary hydrogen spectroscopy experiments. Despite a tremendous amount of experimental and theoretical progress since then, many issues remain unresolved, particularly in the lepton scattering field, and multiple new scattering experiments are currently taking data or under preparation. In this talk, I will briefly review recent progress from lepton scattering experiments, with a focus on the high-precision proton charge radius experiment at Jefferson Lab (PRad). I will also introduce the recently approved PRad-II experiment, which aims to reduce the total uncertainty of rp and the proton electric form factor by about a factor of 4 compared to PRad. This new experiment will be able to push the precision frontier in electromagnetic interaction and contribute to new physics searches such as the violation of Lepton universality.
Biography:
Weizhi Xiong is a professor at Shandong University. He attended University of South Carolina and received a B. S. degree in physics in 2012, and earned a Ph.D. degree from Duke University in 2020. He received the American Physical Society Dissertation Award in Hadronic Physics in 2021, and the 2020 Jefferson Science Associates Thesis Prize. After graduation, he joined Syracuse University and worked as a postdoc researcher between 2020 and 2022. His research focuses mostly on nucleon structure, particularly high-precision measurements of the proton electric charge radius, nucleon electromagnetic form factors, parity-violating deep inelastic scattering, as well as software developments for SoLID spectrometer at Jefferson Lab, and future Electron-Ion Collider in China (EicC).
Online meeting room：https://meeting.tencent.com/dm/eYLJZZnVLcYB （id: 631581681 passcode: 123456）
Host：Prof. Yi-Feng Sun