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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.
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