Baryon Loops Research Articles

Vector-Vector—Pseudoscalar Interactions

Vector-vector\char22{}pseudoscalar (V-V\char22{}PS) intereactions are interpreted exclusively in terms of baryon loops, and application is made to radiative decay of bosons. The model appears to give a highly satisfactory account of $A$-forbiddenness; it also agrees with at least one decay that is $A$-allowed, suggesting that intrinsic V-V\char22{}PS couplings are of secondary importance.

Goldberger-Treiman formulae with Regge phase shifts

If the nucleon-antinuoleon phase shifts display a Regge behaviour as the energy tends to infinity, then the πN-N form factor tends to a constant, and the original derivation of the Goldberger-Treiman formulae for π → ΜΝ and π0→ 2γ fails, because certain crucial dispersion integrals diverge. We rederive the formulae in the original approximation, in which baryon loops dominate, but with the Regge high-energy behaviour. We need assume only that a solution exists; if it does, it is unambiguous and independent of the number of subtractions that may be necessary. But with no subtraction there is a built-in self-consistency criterion which is violated unambiguously in π → ΜΝ. This points to a direct π-lepton coupling; both renormalized and unrenormalized coupling constants are calculated. By including all baryon loops, and using the eightfold way predictions, reasonable if provisional agreement with experiment is obtained for π0 → 2γ. Here the problem of subtractions is less clear-cut. If virtual baryon loops dominate also in η → 2γ, which may be, but need not be, the case, then the partial width is predicted to lie between 30 and 60 eV. Since this is much less than the value recently quoted on different theoretical grounds, a measurement of the width may discriminate between the different physical models for the decay.

Interpretation ofρandζMesons

The $\ensuremath{\rho}$ and $\ensuremath{\zeta}$ mesons are assumed to have the same quantum numbers, $I=J=1$. The $P$-wave pion-pion scattering is then studied in the hope that the two resonances, $\ensuremath{\rho}$ and $\ensuremath{\zeta}$, can be ascribed to the existence of one unstable vector meson $B$ of isospin one. Besides the process $2\ensuremath{\pi}\ensuremath{\rightleftarrows}B$, a strong attractive interaction between pions in the $I=J=1$ state, which is caused by the exchange of $B$ between pions and also by baryon loops, etc., is considered. The pion-pion scattering amplitude is calculated by the chain-diagram approximation and two resonances, which can be identified with the $\ensuremath{\rho}$ and $\ensuremath{\zeta}$ mesons, are obtained. The two resonances in the kaon-pion system are discussed on the same lines.