We study the implications of the flavour SU(3) symmetry for various interpretations (existence of a narrow anti-decuplet resonance, interference of known resonances and a cusp effect) of the neutron ...anomaly in γN → ηN cross section. We show that the explanation of the neutron anomaly due to interference of known N(1535) and N(1650) resonances implies that N(1650) resonance should have a huge coupling to ϕ-meson – at least 5 times larger than the corresponding ρ0 coupling. In terms of quark degrees of freedom that implies that the well-known N(1650) resonance must be a “cryptoexotic pentaquark”– its wave function should contain predominantly an ss̄ component, implying that the N(1650) resonance is dominantly a pentaquark. The explanation of the neutron anomaly as a cusp effect implies very strong violation of the flavour SU(3) symmetry.
Meson loops in the Nambu-Jona-Lasinio model Nikolov, Emil N.; Broniowski, Wojciech; Christov, Christo V. ...
Nuclear physics. A,
10/1996, Letnik:
608, Številka:
4
Journal Article
Recenzirano
The effects of meson loops in the vacuum sector of the Nambu-Jona-Lasinio model are calculated. Using the effective action formalism we take consistently all next-to-leading-order
1
N
c
terms into ...account. This leads to a symmetry-conserving approach, in which all features of spontaneously broken chiral symmetry, such as the Goldstone theorem, the Goldberger-Treiman and the Gell-Mann-Oakes-Renner relations are preserved. Contributions to
〈
qq〉
and
F
π
are calculated, and are shown to be substantial, at the level of 30%, consistent with the
1
N
c
expansion. The leading non-analytic terms in the chiral expansion of
〈
qq〉
,
F
π
and
m
π
have the same form as the one-loop results of chiral perturbation theory.
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