Gravitational form factor $D$ of charmonium from shear stress

TL;DR

This paper calculates the gravitational form factor D of charmonium using shear stress in covariant light front dynamics, validating previous results and analyzing current conservation violations.

Contribution

It introduces a method to extract the D-term from shear stress and compares it with energy density methods, confirming their consistency.

Findings

Violation effects are small in numerical results.

D-term values from shear stress and energy density are consistent.

Validates previous work using different stress-energy tensor components.

Abstract

Based on our recent analysis of the hadronic matrix element of the stress-energy tensor in covariant light front dynamics, we extract the charmonium gravitational form factor $D(Q^2)$ from shear stress $T^{12}$. This is in contrast to our recent work using the (light-front) energy density $T^{+-}$. Indeed, by comparing these two currents, we identify terms that are responsible for the violation of the current conservation. Numerical results based on basis light-front quantization show that the violation effects are small and the $D$-term extracted from the two currents are close to each other, hence validating our previous work using $T^{+-}$.