Consistent meson-field-theoretical description of pp bremsstrahlung

A parameter-free and relativistic extension of the RuhrPot meson-baryon model is used to define the dominant isoscalar meson-exchange currents. We compute pp-bremsstrahlung observables below the π-production threshold using a relativistic hadronic current density that includes impulse, wave function reorthonormalization, meson-recoil, N¯N creation and annihilation, ρπγ + ωπγ + ρηγ + ωηγ vector-meson decay, and NΔγ(π,ρ) exchange currents. We obtain a good description of the available data. The NΔγ(π) current is shown to dominate the large two-body contributions and closed-form expressions for various nonrelativistic approximations are analyzed. An experimental sensitivity to the admixture of pseudoscalar and pseudovector admixture of the NNπ interaction is demonstrated. We examine the Lorentz invariance of the NN⇄NN t matrices and show a dominantly pseudovector NNπ coupling renders impulse approximation calculations without boost operators to be essentially exact. Conversely, a similar analysis of the ΔN⇄NN transitions shows that boost operators and the two-body NΔγ wave function reorthonormalization meson-recoil currents are required in NN, ΔN, and ΔΔ coupled channel t-matrix applications. The need for additional data is stressed. © 1996 The American Physical Society.