Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 66: Hadronic Probes VII, Bremsstrahlung

HK 66.1: Group Report

Thursday, March 19, 1998, 14:00–14:30, G

What can we learn from Proton-proton Bremsstrahlung?^† — •J.A. Eden, C. Arias Tobena, S. Deister, and M.F. Gari — Institut f"ur Theoretische Physik, Ruhr-Universit"at Bochum, Universit"atstr 150, , D-44780 Bochum

We present a meson field-theoretical analysis of the high-quality proton-proton bremsstrahlung data that has recently been made available from COSY [1], Uppsala [2] and KVI [3]. In order to do that, we first describe how the RuhrPot model combines a Hamilton formalism with a meson field theory [4] to obtain a non-perturbative and self-consistent prescription for the microscopic calculation of the meson-baryon form factors [5], the NN- [6] and 3N- [4] interactions, electromagnetic form factors [7] and meson-exchange currents [8-10].

We show that unitarity demands the inclusion of wave function re-orthonormalization and meson-recoil dynamics in the complete current operator - and we present calculations to establish that the effects in the observables can be significant. (Analogous effects vanish in the 3N force but persist in the two-boson exchange potential [4].) By contrast, we demonstrate that the Z-graphs contributions to the observables are essentially negligible below the pion production threshold. After investigating the importance of the CM motion for a non-covariant t-matrix, we explore the model dependence of the dominant exchange currents by probing the relationships between coupling constants and form factors that exist in both the NN- interaction and the exchange currents. Finally, we present preliminary calculations for exchange currents involving the gauge invariant coupling of a photon to the NN-pion form factor and summarize the progress and challenges remaining to extend the predictive power of the calculations to higher energies.

0.2 true cm ^†This work is supported by COSY-KFA Juelich (41140512). 0.2 true cm

[1] H. Herman, for COSY-TOF Collaboration, priv. comm.

[2] J. Zlomanczuk, for UPPSALA Collaboration, priv. comm.

[3] H. Huisman, for SALAD and TAPS Collaboration, priv. comm.

[4] J. A. Eden and M. F. Gari, Phys. Rev. C53, 1510 (1996).

[5] J. Flender and M. F. Gari, Phys. Rev. C51, R1 (1995); Z. Phys. A343, 467 (1992).

[6] D. Plumper, J. Flender and M. F. Gari, Phys. Rev. C49, 2370 (1994).

[7] S. Deister, Ph.D Thesis, Ruhr-Uni Bochum 1996, (unpublished).

[8] J. A. Eden and M. F. Gari, Phys. Lett. B347, 187 (1995).

[9] J. A. Eden and M. F. Gari, JETP 83, 642 (1996).

[10] J. A. Eden and M. F. Gari, Phys. Rev. C53, 1102 (1996).