The proton radius puzzle questions the self-consistency of theory and experiment in light muonic and electronic bound systems. Here we summarize the current status of virtual particle models as well as Lorentz-violating models that have been proposed in order to explain the discrepancy. Highly charged one-electron ions and muonic bound systems have been used as probes of the strongest electromagnetic fields achievable in the laboratory. The average electric field seen by a muon orbiting a proton is comparable to hydrogenlike uranium and, notably, larger than the electric field in the most advanced strong-laser facilities. Effective interactions due to virtual annihilation inside the proton (lepton pairs) and process-dependent corrections (nonresonant effects) are discussed as possible explanations of the proton size puzzle. The need for more experimental data on related transitions is emphasized.



Keywords and Phrases

Atomic Physics; Cesium; Cooling; Frequencies; Ground State; Hydrogen; Light Absorption; Magnetic Moments; Photodiodes; Rubidium; Ultrahigh Vacuum; Ultraviolet Radiation; Einstein's Equivalence Principle (EEP); Hyperfine Transitions; Radio Frequencies (RF); Transition Frequencies; Quantum Theory

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

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© 2015 American Physical Society (APS), All rights reserved.

Publication Date

01 Jul 2015

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Physics Commons