Lepton universality test in the photoproduction of $e^{-}{e}^{+}$ versus ${\mu }^{-}{\mu }^{+}$ pairs on a proton target

Abstract

In view of the significantly different proton charge radius extracted from muonic hydrogen Lamb shift measurements as compared to electronic hydrogen spectroscopy or electron scattering experiments, we study in this work the photoproduction of a lepton pair on a proton target in the limit of very small momentum transfer as a way to provide a test of the lepton universality when extracting the proton charge form factor. By detecting the recoiling proton in the $\gamma p\to l^{-}{l}^{+}p$ reaction, we show that a measurement of a ratio of $e^{-}{e}^{+}+{\mu }^{-}{\mu }^{+}$ over $e^{-}{e}^{+}$ cross sections with a relative precision of around 2%, would allow for a test to distinguish between the two different proton charge radii currently extracted from muonic and electronic observables.

4 pages, 4 figures, version to be published in Phys. Rev. Lett

References in corpus (7)

• High-precision determination of the electric and magnetic form factors of the proton
• The electric and magnetic form factors of the proton
• The Proton Radius Puzzle
• Muonic hydrogen and MeV forces
• New Parity-Violating Muonic Forces
• Proton size anomaly
• Evaluation of the proton charge radius from e-p scattering

Cited by in corpus (12)

• The proton charge radius
• Nucleon Polarizabilities: from Compton Scattering to Hydrogen Atom
• Expanding Nuclear Physics Horizons with the Gamma Factory
• The proton radius (puzzle?) and its relatives
• Review of experimental and theoretical status of the proton radius puzzle
• Two-photon exchange correction to muon-proton elastic scattering at low momentum transfer
• Dispersion relation formalism for the two-photon exchange correction to elastic muon-proton scattering: elastic intermediate state
• Leading order corrections to the Bethe-Heitler process in the $\gamma p\to l^{+}{l}^{-}p$ reaction
• Soft-photon corrections to the Bethe-Heitler process in the $\gamma p\to l^{+}{l}^{-}p$ reaction
• Low energy doubly-virtual Compton scattering from di-lepton electroproduction on a nucleon
• Leading-order QED radiative corrections to timelike Compton scattering on the proton
• Dilepton photoproduction on a deuteron target