\( \newcommand{\dd}{\mathrm{d}} \) \( \DeclareMathOperator{\sign}{sign} \)

HIC for FAIR logo Nuclear Physics Colloquium

Venue: Physics Building, Max-von-Laue-Str. 1, Seminar Room PHYS 2.116
Time: Friday, May 19, 10:00am (s.t.)
Contact: hees@fias.uni-frankfurt.de

Proton remains puzzling

Haiyan Gao (Duke University)

Nucleons are building blocks of visible matter, and are responsible for more than 99% of the visible mass in the universe. Despite major progress made in the last two decades in understanding the proton spin "crisis",  discovered in the late 1980s by the European Muon Collaboration, the proton spin remains puzzling. At the same time, a new proton puzzle developed in the last several years concerning the proton charge radius, which is the charge weighted size of the proton. The ultrahigh precise value of the proton charge radius determined from muonic hydrogen Lamb shift measurements is about $7\sigma$ smaller than the values determined from electron-proton scattering experiments and the CODATA value of the hydrogen Lamb shift measurements. In this talk I will review the latest situation concerning the proton spin and charge radius and discuss the 12 GeV SoLID project at Jefferson Lab and the PRad experiment, that was completed recently.

Nuclear Physics Colloquium Homepage