Chiral dynamics and the S11(1535) nucleon resonance

Abstract

The SU (3) chiral effective lagrangian at next-to-leading order is applied to the S-wave meson-baryon interaction in the energy range around the ηN threshold. Potentials are derived from this lagrangian and used in a coupled channel calculation of the πN , ηN , KΛ, KΣ system in the isospin-1/2, l = 0 partial wave. Using the same parameters as obtained from a fit to the low energy KN data it is found that a quasi-bound KΣ-state is formed, with properties remarkably similar to the S 11 (1535) nucleon resonance. In particular, we find a large partial decay width into ηN consistent with the empirical data.

The impact of chirally odd condensates on the rho meson

“…For the physics of resonances the connection is even more loose. There are recent approaches which explain some hadronic resonances as dynamically generated from chiral dynamics [15][16][17][18][19][20][21], but again this primarily points towards an intimate connection between hadron physics and chiral symmetry breaking and not so much chiral restoration. As suggested, e.g., in [2,22] the link to chiral restoration might be indirect: The in-medium broadening could be understood as a step towards deconfinement.…”

“…The running coupling has to be evaluated at the scale M. has been extracted from the experimental difference between vector and axial-vector spectral information [48]. We use the result of [41] O br 4 vac ≈ 9 7 qq 2 vac (15) together with the vacuum ρ-meson properties [57] to fix the vacuum value for O sym 4 defined in (13). For the pure chiral restoration scenario one drops then the chiral symmetry breaking terms, in particular (14).…”

“…Thus also here one only needs the vacuum values for the chirally invariant terms, in particular for (13). We recall that (15) indicates that the chiral symmetry breaking four-quark condensate factorizes [41].…”

Photo- and electro-production of mesons on nucleons and nuclei

“…The interaction of the octet of pseudoscalar mesons with the octet of stable baryons has been the object of much theoretical study [4,5,6,7,9,10,11,12,13,14,15,16,17,18]. One of the common features of these studies is the dynamical generation of some resonances which appear as a consequence of the interaction of the mesons and baryons in coupled channels, forming some kind of molecular state, quite different for the ordinary three quark states associated to the baryons.…”

Nucleon resonance production in K+N interactions

“…In Ref. [2], the authors argued that the N * (1535) is a KΣ − KΛ molecular state. In this picture, large couplings of the N * (1535) with the KΣ and KΛ channels are expected [3].…”