Taming the Pion Cloud of the Nucleon

TL;DR

This paper calculates the pion contribution to the nucleon self-energy using a model-independent light-front approach, aligning with chiral perturbation theory and lattice QCD, and relates it to experimental observations of pion content.

Contribution

It provides a model-independent, light-front calculation of the pion contribution to nucleon self-energy constrained by experimental data.

Findings

Pion mass dependence of self-energy matches chiral perturbation theory at small μ.

Linear μ dependence of self-energy at larger μ agrees with lattice QCD.

Derivative of self-energy relates to pion content and experimental antiquark asymmetry.

Abstract

We present a light-front determination of the pionic contribution to the nucleon self-energy, $\Sigma_\pi$, to second-order in pion-baryon coupling constants that allows the pion-nucleon vertex function to be treated in a model-independent manner constrained by experiment. The pion mass $\mu$ dependence of $\Sigma_\pi$ is consistent with chiral perturbation theory results for small values of $\mu$ and is also linearly dependent on $\mu$ for larger values, in accord with the results of lattice QCD calculations. The derivative of $\Sigma_\pi$ with respect to $\mu^2$ yields the dominant contribution to the pion content, which is consistent with the $\bar{d}-\bar{u}$ difference observed experimentally in the violation of the Gottfried sum rule.