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HK: Hadronen und Kerne

HK 67: Structure of Baryons, Mesons IX, Theory

HK 67.5: Talk

Thursday, March 19, 1998, 15:30–15:45, H

Diquark confinement in an extended NJL model^* — •G. Hellstern, R. Alkofer, and H. Reinhardt — Institute for Theoretical Physics, Auf der Morgenstelle 14, 72076 T"ubingen

In a Nambu–Jona-Lasinio model supplemented with an infrared cutoff we study the issue whether diquarks are confined when the model is extended beyond the rainbow-ladder approximation, as conjectured in ref. [1]. The gap equation, obtained in a truncation scheme motivated via a nontrivial quark-gluon vertex function, is solved to determine the constituent quark mass if chiral symmetry is spontaneously broken. In a second step, the Bethe-Salpeter equations for mesons and diquarks beyond ladder approximation are derived, taking care to preserve Goldstone’s theorem in the pion channel. While the obtained masses of pseudoscalar and vector mesons are only moderately shifted compared to the values in ladder approximation, we observe that scalar diquarks disappear from the physical spectrum and therefore are confined [2].

(*) Supported by BMBF under contract 06TU888.

[1] A. Bender, C. D. Roberts, L. v. Smekal, Phys. Lett. B380, 7 (1996).

[2] G. Hellstern, R. Alkofer, H. Reinhardt, e-print hep-ph/9706551,
Nucl. Phys. A in press.