Scale-anomaly-induced binding pressure in hadrons

TL;DR

The work studies how the QCD scale anomaly, via the trace part of the energy-momentum tensor, shapes the internal stress distributions of hadrons through gravitational form factors. Using model-independent GFFs from dispersion relations, it computes three-dimensional instant-form and two-dimensional light-front densities with a multipole extrapolation $F(t)=F(0)/(1+t/\Lambda^2)^m$. The main finding is that the scale-anomaly contribution, encoded in the trace part, yields negative binding pressure $\hat{p}$ for both the pion and the nucleon across instant and light-front forms, suggesting a universal, model-independent confinement mechanism. These results point to a form-independent role of the scale anomaly in hadron stability and motivate further studies of additional hadrons and connections to generalized parton distributions.

Abstract

The effect of the QCD scale anomaly on the internal pressure distribution of hadrons is studied based on the trace-traceless decomposition of the energy-momentum tensor. Using recent model-independent results of gravitational form factors as input, the pressure distributions of both pions and nucleons are analyzed in the instant form and the light-front form. It is found that, in all cases, the scale anomaly dominantly generates the negative binding pressure. This result suggests that the phenomenon is a universal feature, independent of models, types of hadrons, and the choice of form.

Figures (2)

• Figure 1: Pressure decomposition for pions.
• Figure 2: Pressure decomposition for nucleons.