The proton radius (puzzle?) and its relatives

2021/06/30 by Clara Peset, Antonio Pineda, Oleksandr Tomalak
Engineering · Physics and Astronomy · #Atomic and Molecular Physics #Charge radius #Electron #Field (mathematics) #Lepton #Nuclear physics #Observable #Particle Accelerators and Free-Electron Lasers #Particle physics #Physics #Proton #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum electrodynamics #Quantum mechanics #RADIUS #Scattering #Theoretical physics #hep-ph #nucl-th #physics.atom-ph

paper · pdf · doi:10.1016/j.ppnp.2021.103901

70 pages, 14 figures. Minor modifications to meet journal version. References added

openalex publication_date 2021/08/16 · arxiv created 2021/09/03 · arxiv updated 2021/10/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We review determinations of the electric proton charge radius from a diverse set of low-energy observables. We explore under which conditions it can be related to Wilson coefficients of appropriate effective field theories. This discussion is generalized to other low-energy constants. This provides us with a unified framework to deal with a set of low-energy constants of the proton associated with its electromagnetic interactions. Unambiguous definitions of these objects are given, as well as their relation with expectation values of QCD operators. We show that the proton radius obtained from spectroscopy and lepton-proton scattering (when both the lepton and proton move with nonrelativistic velocities) is related to the same object of the underlying field theory with \cal O(α) precision. The model dependence of these analyses is discussed. The prospects of constructing effective field theories valid for the kinematic configuration of present, or near-future, lepton-proton scattering experiments are discussed.

Citations

• Three-loop QED Vacuum Polarization and the Four--loop Muon Anomalous Magnetic Moment
• Learning about the chiral structure of the proton from the hyperfine splitting
• Radiative-nonrecoil corrections of orderα2(Zα)5to the Lamb shift
• Radiative energy shifts induced by local potentials
• Leading chiral logarithms to the hyperfine splitting of the hydrogen and muonic hydrogen
• Review of Heavy Quarkonium at weak coupling
• The RMS charge radius of the proton and Zemach moments
• Higher-order nuclear-polarizability corrections in atomic hydrogen
• Proton Structure from the Measurement of 2S-2P Transition Frequencies of Muonic Hydrogen
• Higher-order binding corrections to the Lamb shift of 2Pstates
• The infrared divergence phenomena and high-energy processes
• Proton-polarizability effect in the Lamb shift for the hydrogen atom
• Theory of Light Hydrogenlike Atoms
• Radiative corrections to electron-proton scattering
• Lepton Universality Test in the Photoproduction ofe−e+Versusμ−μ+Pairs on a Proton Target
• The size of the proton
• CODATA recommended values of the fundamental physical constants: 2010
• The Proton Radius Puzzle
• Technical Design Report for the Paul Scherrer Institute Experiment R-12-01.1: Studying the Proton "Radius" Puzzle with μp Elastic Scattering
• Theory of the Lamb shift in hydrogen and light hydrogen-like ions
• Defining the proton radius: A unified treatment
• CODATA recommended values of the fundamental physical constants: 2006
• Review of Particle Physics
• Letter of Intent: A New QCD facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)
• Big-Bang Nucleosynthesis