Generalized parton distributions of the nucleon in the chiral quark soliton model II: Chiral anomaly mediation in the polarized GPDs

Abstract

We calculate the polarized flavor-singlet generalized parton distributions (GPDs) $\widetilde H^{u+d}$ and $\widetilde E^{u+d}$ in the chiral quark soliton model at nonzero skewness and momentum transfer. Results are obtained with and without a singlet pseudoscalar meson $η_0$, whose mass is generated by the chiral anomaly. Relative to the pion-only model, the singlet field introduces a sizable contribution to $\widetilde E^{u+d}$ in the ERBL region but only a minor correction to $\widetilde H^{u+d}$. An explicit meson-exchange term qualitatively accounts for this contrast and displays the anticipated singlet pole. When the anomaly-induced mass is set to zero, the pole becomes massless, and the exchange term dominates $\widetilde E^{u+d}$ at small momentum transfer. These findings demonstrate how anomalous singlet-meson dynamics leaves distinct signatures in the polarized GPDs of the nucleon.