Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 66: Hadronic Probes VII, Bremsstrahlung
HK 66.3: Talk
Thursday, March 19, 1998, 15:00–15:15, G
Effects of relativity in proton-proton bremsstrahlung — •O. Scholten1, G.H. Martinus1, and J. Tjon2 — 1Kernfysisch Versneller Instituut, 9747 AA Groningen, the Netherlands — 2Institute for Theoretical Physics, University of Utrecht, 3508 TA Utrecht, the Netherlands
We investigate the influence of negative-energy states in proton-proton bremsstrahlung in a fully relativistic framework using the T-matrix of Fleischer and Tjon. The contribution from negative-energy states in the single-scattering diagrams is shown to be large, indicating that relativistic effects are important. The rescattering contribution compensates some of the effect, which is shown to be a consequence of a low-energy theorem. The net effect of negative-energy states nevertheless is of the order of 20 % at higher energies. We investigate retardation effects in the NN interaction by means of a one-pion exchange model, which gives effects of the order of 15 % at the pion-production threshold. We furthermore modify the NN T-matrix to incorporate some of these effects, and find that on the level of single-scattering contributions they are of the order of 10 percent. Meson-exchange currents and the Δ-isobar have been included in the calculations.
We show predictions at incoming proton energy Elab=190 MeV, upto Elab=400 MeV. Relativistic effects and the contribution from the Δ are increasing with energy, but even at the lowest energy considered these effects are sizable as compared to the leading-order nucleonic current.