Spin structure of the pion from the instanton vacuum

TL;DR

This paper explores the spin structure of the pion using a nonlocal chiral quark model from the instanton vacuum, calculating tensor form factors and quark density distributions, and comparing results with lattice data.

Contribution

It provides the first evaluation of pion tensor form factors for the first and second moments within this model and compares them with lattice results.

Findings

Tensor form factors agree with lattice data

Probability density of transversely polarized quarks matches lattice results

Distribution distortion of quarks in the transverse plane is analyzed

Abstract

We investigate the spin structure of the pion within the framework of the nonlocal chiral quark model from the instanton vacuum. We first evaluate the tensor form factors of the pion for the first and second moment (n=1,2) and compare it with the lattice data. Combining the tensor form factor of the pion with the electromagnetic one, we determine the impact-parameter dependent probability density of transversely polarized quarks inside the pion. It turns out that the present numerical results for the tensor form factor as well as those for the probability density are in good agreement with the lattice data. We also discuss the distortion of the spatial distribution of the quarks in the transverse plane inside the pion.