Consistent meson-field-theoretical description ofppbremsstrahlung

Abstract

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 \ensuremath{\pi}-production threshold using a relativistic hadronic current density that includes impulse, wave function reorthonormalization, meson-recoil, N\ifmmode\bar\else\textasciimacron\fi{}N creation and annihilation, \ensuremath{\rho}\ensuremath{\pi}\ensuremath{\gamma} + \ensuremath{\omega}\ensuremath{\pi}\ensuremath{\gamma} + \ensuremath{\rho}\ensuremath{\eta}\ensuremath{\gamma} + \ensuremath{\omega}\ensuremath{\eta}\ensuremath{\gamma} vector-meson decay, and N\ensuremath{\Delta}\ensuremath{\gamma}(\ensuremath{\pi},\ensuremath{\rho}) exchange currents. We obtain a good description of the available data. The N\ensuremath{\Delta}\ensuremath{\gamma}(\ensuremath{\pi}) 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 NN\ensuremath{\pi} interaction is demonstrated. We examine the Lorentz invariance of the NN\ensuremath{\rightleftarrows}NN t matrices and show a dominantly pseudovector NN\ensuremath{\pi} coupling renders impulse approximation calculations without boost operators to be essentially exact. Conversely, a similar analysis of the \ensuremath{\Delta}N\ensuremath{\rightleftarrows}NN transitions shows that boost operators and the two-body N\ensuremath{\Delta}\ensuremath{\gamma} wave function reorthonormalization meson-recoil currents are required in NN, \ensuremath{\Delta}N, and \ensuremath{\Delta}\ensuremath{\Delta} coupled channel t-matrix applications. The need for additional data is stressed. \textcopyright{} 1996 The American Physical Society.