Orbital structure of quarks inside the nucleon in the light-cone diquark model

TL;DR

This paper investigates the orbital angular momentum distribution of quarks inside the proton using a light-cone diquark model, calculating generalized parton distributions and impact parameter dependence to reveal spatial and momentum characteristics.

Contribution

The study introduces a detailed calculation of quark GPDs and OAM distributions within the light-cone diquark model, highlighting the sign difference of $E_q$ for u and d quarks and the impact parameter dependence of OAM.

Findings

$E_u$ and $E_d$ have opposite signs with similar magnitude.

$L_u(x)$ is positive, while $L_d(x)$ is near zero.

Impact parameter dependence of quark OAM is axially symmetric.

Abstract

We study the orbital angular momentum structure of the quarks inside the proton. By employing the light-cone diquark model and the overlap representation formalism, we calculate the chiral-even generalized parton distribution functions (GPDs) $H_q(x,\xi,\Delta^2)$, $\widetilde{H}_q(x,\xi,\Delta^2)$ and $E_q(x,\xi,\Delta^2)$ at zero skewedness for $q=u$ and $d$ quarks. In our model $E_u$ and $E_d$ have opposite sign with similar size. Those GPDs are applied to calculate the orbital angular momentum (OAM) distributions, showing that $L_u(x)$ is positive, while $L_d(x)$ is consistent with zero compared with $L_u(x)$. We introduce the impact parameter dependence of the quark OAM distribution. It describes the position space distribution of the quark orbital angular momentum at given $x$. We found that the impact parameter dependence of the quark OAM distribution is axially symmetric in the light-cone diquark model.