Quantum interferences in the $\gamma N\to e^{+}{e}^{-}N$ reaction close to the vector meson production threshold

Abstract

The exclusive photoproduction of $e^{+}{e}^{-}$ pairs from nucleons close to the vector meson production threshold ($1.4<\sqrt{s}<1.8$ GeV) results from two main processes: the emission of Bethe-Heitler pairs and the photoproduction of ${\rho }^0$- and $\omega$-mesons decaying into $e^{+}{e}^{-}$ pairs. The Bethe-Heitler amplitudes are purely electromagnetic and reflect mostly the nucleon magnetic structure. The $\gamma N\to e^{+}{e}^{-}N$ amplitudes arising from vector meson production and decay are derived from $\gamma N\to {\rho }^{0}N$ and $\gamma N\to \omega N$ amplitudes supplemented by the Vector Meson Dominance assumption. The vector meson photoproduction amplitudes are calculated using a relativistic and unitary coupled-channel approach to meson-nucleon scattering. They depend sensitively on the coupling of vector fields to baryon resonances. The $\gamma N\to e^{+}{e}^{-}N$ differential cross sections display interference patterns. The interference of Bethe-Heitler pair production with vector meson $e^{+}{e}^{-}$ decay is quite small in the domain of validity of our model for all angles of the emitted $e^{+}{e}^{-}$ pair. The interference of ${\rho }^0$- and $\omega$-mesons in the $e^{+}{e}^{-}$ channel can be large. It is constructive for the $\gamma p\to e^{+}{e}^{-}p$ reaction and destructive for the $\gamma n\to e^{+}{e}^{-}n$ reaction. We discuss the shape and magnitude of the $e^{+}{e}^{-}$ pair spectra produced in the $\gamma p\to e^{+}{e}^{-}p$ and $\gamma n\to e^{+}{e}^{-}n$ reactions as functions of the pair emission angle and of the total center of mass energy $\sqrt{s}$.

28 pages, 12 figures

References in corpus (4)

• Relativistic chiral SU(3) symmetry, large N_c sum rules and meson-baryon scattering
• Nucleon Charge and Magnetization Densities from Sachs Form Factors
• Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q**2 = 1.0 GeV**2
• Quantum interference of rho0- and omega-mesons in the pi N -> e+e- N reaction

Cited by in corpus (7)

• A QCD analysis of near-threshold quarkonium leptoproduction at large photon virtualities
• Dilepton Radiation from Strongly Interacting Systems
• Di-Electrons from Resonances in Nucleon-Nucleon Collisions
• Medium Effects in rho-Meson Photoproduction
• Medium Modifications of the Rho Meson in Nuclear Photoproduction
• Semihadronic and hadronic decays of ${\rho }^0$ and $\omega$ mesons coherently photoproduced in the isoscalar nuclei
• Pion exchange interaction in the $\gamma p\to p{e}^{+}{e}^{-}$ reaction