Generalized parton distributions of the kaon and pion within the nonlocal chiral quark model

TL;DR

This study investigates the generalized parton distributions of kaon and pion using a nonlocal chiral quark model, analyzing their properties, evolution, and form factors, revealing asymmetries and confinement effects.

Contribution

It provides a detailed analysis of kaon and pion GPDs within the nonlocal chiral quark model, including their evolution and form factors, highlighting the impact of quark mass asymmetry.

Findings

Kaon GPDs show significant distortion near ξ=1 due to quark mass asymmetry.

Sea quarks and gluons are suppressed as ξ increases, confined within the ERBL region.

Calculated gravitational form factor ratios for the kaon are provided and compared with other models.

Abstract

In the present study, we explore the properties of generalized parton distributions (GPDs) for the kaon and pion within the framework of the nonlocal chiral quark model (NL$\chi$QM). Valence quark GPDs of the kaon and pion are analyzed with respect to their momentum fraction $x$ and skewness $\xi$ dependencies in the DGLAP and ERBL regions. We observe that the asymmetry of the current quark masses in kaon results in a significant distortion of the quark GPDs in kaon near $\xi=1$, compared to the case of the pion. The quark GPDs of the kaon and pion are evolved to $\mu^2 = 4$ GeV$^2$ and 100 GeV$^2$ by the QCD evolution equation at one-loop order using the \texttt{APFEL++} package. We find that the produced sea quarks and gluons are largely suppressed as $\xi$ becomes nonzero, predominantly confined within the ERBL region. We subsequently examine the polynomiality of the GPDs and numerically obtain the electromagnetic and gravitational form factors of the kaon and pion. For the kaon, gravitational form factor ratios $A_{\bar s/K^+}(0)/A_{s/K^+}(0) = 1.26$ and $D_{\bar s/K^+}(0)/D_{s/K^+}(0) = 1.10$ are reported and compared with results from other effective models.