The Proton Radius Puzzle

@article{Carlson2015ThePR,
  title={The Proton Radius Puzzle},
  author={C. Carlson},
  journal={Progress in Particle and Nuclear Physics},
  year={2015},
  volume={82},
  pages={59-77}
}
  • C. Carlson
  • Published 2015
  • Physics
  • Progress in Particle and Nuclear Physics
Abstract The proton size, specifically its charge radius, was thought known to about 1% accuracy. Now a new method probing the proton with muons instead of electrons finds a radius about 4% smaller, and to boot gives an uncertainty limit of about 0.1%. We review the different measurements, some of the calculations that underlie them, some of the suggestions that have been made to resolve the conflict, and give a brief overview new related experimental initiatives. At present, however, the… Expand

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References

SHOWING 1-10 OF 170 REFERENCES
Toward a resolution of the proton size puzzle
We show that off-mass-shell effects arising from the internal structure of the proton provide a new proton polarization mechanism in the Lamb shift, proportional to the lepton mass to the fourthExpand
The size of the proton: Closing in on the radius puzzle
We analyze the recent electron-proton scattering data from Mainz using a dispersive framework that respects the constraints from analyticity and unitarity on the nucleon structure. We also perform aExpand
Proton radius puzzle and large extra dimensions
We propose a theoretical scenario to solve the proton radius puzzle which recently arises from the muonic hydrogen experiment. In this framework, 4 + n dimensional theory is incorporated withExpand
Muonic Hydrogen and the Proton Radius Puzzle
The extremely precise extraction of the proton radius obtained by Pohl et al. from the measured energy difference between the 2P and 2S states of muonic hydrogen disagrees significantly with thatExpand
Proton size anomaly.
TLDR
It is found that the many constraints from low energy data disfavor new spin-0, spin-1, and spin-2 particles as an explanation for the Lamb shift in muonic hydrogen. Expand
The PRad experiment and the proton radius puzzle
New results from the recent muonic hydrogen experiments seriously questioned our knowledge of the proton charge radius, rp. The new value, with its unprecedented less than sub-percent precision, isExpand
Some issues concerning the proton charge radius puzzle
p i 1=2 derived from electron scattering and from the Lamb shift of muonic hydrogen has caused a considerable worry in the physics community. Since the Lamb shift is a corner stone of the tests ofExpand
Studying the proton "radius" puzzle with μp elastic scattering
The disagreement between the proton radius determined from muonic hydrogen and from electronic measurements is called the proton radius puzzle. The resolution of the puzzle remains unclear andExpand
The MUSE Experiment: Studying the Proton Radius Puzzle with muon-proton Elastic Scattering
The Proton Radius Puzzle refers to the disagreement between the proton charge radius determined from muonic hydrogen and the radius determined from atomic hydrogen level transitions and ep elasticExpand
On the RMS radius of the proton
Abstract We study the world data on elastic electron–proton scattering in order to determine the proton charge rms-radius. After accounting for the Coulomb distortion and using a parameterizationExpand
...
1
2
3
4
5
...