Skewness dependence of the pion and kaon generalized parton distributions

Abstract

We investigate the skewness dependence of the pion generalized parton distribution (GPD) at different momentum transfers $-t$ within the covariant Nambu-Jona-Lasinio (NJL) model, employing the Schwinger proper-time regularization scheme to regulate ultraviolet divergences and implement an effective description of quark confinement. We evolve the pion GPDs for various values of $-t$ and $\xi$ to the scales $\mu^2=4$ and $27~\mathrm{GeV}^2$. We find that the valence-quark distributions are suppressed with increasing $-t$ and $\xi$, with the suppression becoming more pronounced at the lower scale, $\mu^2=4~\mathrm{GeV}^2$. In the forward limit, $\xi=0$ and $-t=0$, the predicted pion valence-quark distribution at $\mu^2=27~\mathrm{GeV}^2$ is in good agreement with the available experimental data and the global JAM analysis. The corresponding pion gluon distribution at $\mu^2=4~\mathrm{GeV}^2$, obtained through next-to-leading-order (NLO) DGLAP evolution, is also consistent with the JAM analysis. We further find that the pion and kaon valence-quark distributions exhibit a strong dependence on $-t$ but only a weak dependence on $\xi$, whereas the corresponding gluon distributions show weak dependence on both $-t$ and $\xi$. The generalized form factors of the pion and kaon at $\mu^2=4~\mathrm{GeV}^2$ are in good agreement with the corresponding lattice-QCD results.