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HK: Hadronen und Kerne
HK 22: Schwache Wechselwirkungen, fundamentale Symmetrien II
HK 22.5: Talk
Tuesday, March 25, 1997, 15:30–15:45, HS D
Is the η Meson a Goldstone Boson ? — •Mariana Kirchbach — Institut f"ur Kernphysik, Universit"at Mainz, D-55099 Mainz, Germany
The decoupling of the η meson from the nucleon, as recently concluded from analyzing p p collisions [1] and η photoproduction off proton at threshold [2], leads to a vanishing contribution of the η pole term to the hypercharge nucleon axial vector current Jµ ,5(8). No partial conservation of the latter can be achieved, therefore. The suppressed η N coupling constant can be understood if the hypercharge and the singlet axial vector currents are ideally mixed, as are those of the electroweak gauge theory. In that case universality of the couplings of isoscalar 0− and 1+ mesons to arbitrary hadron targets can be motivated. If so, the η - and f1 NN vertex constants will appear proportional to Δ s, the fraction of nucleon spin carried by the strange quark sea, thus explaining their suppression naturally [3], [4]. The ideal mixing of the hypercharge and singlet axial currents prevents the f1(1285) meson of being the chiral partner to the ω meson and thus seriously questions the validity of chiral SU(3)L⊗ SU(3)R rotations in three-flavor space as symmetry transformations of the QCD Lagrangian.
[1] W. Grein and P. Kroll, Nucl. Phys. A338 (1980) 332.
[2] L. Tiator, C. Bennhold, and S. Kamalov, Nucl. Phys. A580 (1994) 455.
[3] M. Kirchbach and L. Tiator, Nucl. Phys. A604 (1996) 385.
[4] M. Kirchbach and D.O. Riska, Nucl. Phys. A594 (1995) 419.