Physics Colloquium

"The Proton Remains Puzzling"

Presented by Haiyan Gao, Duke University

Tuesday, January 7, 2020, 3:30 pm — Large Seminar Room, Bldg. 510

Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99% of the visible matter in the universe. Despite decades of efforts in studying its internal structure, there are still a number of puzzles surrounding the proton such as its spin, mass, and charge radius. The proton charge radius puzzle developed about ten years ago refers to a 5-7 sigma discrepancy between the ultrahigh precise values of the proton charge radius determined from muonic hydrogen Lamb shift measurements and the CODATA values compiled from electron-proton scattering experiments and hydrogen spectroscopy measurements. In this talk I will briefly introduce the proton spin and mass puzzles first. I will then focus on the proton charge radius puzzle, the latest experimental results, and especially the PRad experiment at Jefferson Lab and its result.

Hosted by: Xin Qian

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