P03model and helicity structure of photoproduction couplings

Abstract

Neglecting the $\Delta L_3=2\mathrm{}$ term within the possible algebraic structure in a 35-dimensional $\mathrm{SU}{\mathrm{}\left(6\right)\mathrm{}}_W$ representation for the magnetic-dipole operator is shown to result in the ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ model for photodecays of nucleon resonances. We then expand the reduced $L_3$-changing amplitudes into partial waves and impose a simple $\mathrm{SU}{\mathrm{}\left(6\right)\mathrm{}}_W\times \mathrm{O}{\mathrm{}\left(2\right)\mathrm{}}_{L_3}$ constraint on the $W=1\mathrm{}$ and $W=0\mathrm{}$ parts of the 35. This leads to several more relations among helicity amplitudes for these decays. Using vector dominance and the partial-wave parameters from resonance decays into the lowest-mass meson 35-plet, pseudoscalar decays in particular, we get photodecay couplings which are in good agreement with partial-wave analysis.