Pion gravitational form factors in the QCD instanton vacuum II

TL;DR

This paper investigates the pion gravitational form factors using QCD instanton vacuum techniques, incorporating novel semi-hard contributions, and compares the results with lattice data and other theoretical models to analyze the internal pressure and shear distributions within the pion.

Contribution

It introduces a new semi-hard contribution to the pion GFFs calculated within the QCD instanton vacuum, enhancing understanding of pion structure.

Findings

Semi-hard instanton contributions significantly affect pion GFFs.

Results align well with lattice QCD data.

Derived internal pressure and shear distributions within the pion.

Abstract

We revisit the hard QCD contributions to the pion gravitational form factors (GFFs), in terms of the twist-2,3 pion distribution amplitudes (DA), including novel semi-hard contributions from the instantons. The pion DAs are evaluated in the QCD instanton vacuum, and then properly evolved to higher resolution. The results are compared to our recent results from the QCD instanton vacuum, as well as Bethe-Salpeter calculations and recent lattice data. The interpolated hard and soft contributions to the pion D-form-factor, are used to derive the (gravitational) pressure and shear within the pion, with a clear delineation of their range.