On the shape of nucleons at high energies

TL;DR

This paper models how nucleon shapes evolve at high energies, showing spheroid expansion, a transition to correlated parton behavior, and the formation of a hollow core as energy increases, with estimates of parameters.

Contribution

It introduces a model describing the energy-dependent shape evolution of nucleons, incorporating transverse parton motion and correlations, extending previous descriptions.

Findings

Nucleons become spheroids expanding with √lnE transversely.

Longitudinal growth halts due to parton correlations.

A hollow core forms inside nucleons at very high energies.

Abstract

A scenario of evolution of the shape of nucleons with increasing energy is described in the framework of extended parton model, which consistently takes into account the transverse motion of the partons. At the energy $E$ up to LHC, the nucleons have the form of a spheroid which expands as $\sqrt{\ln \!E}$ in the transverse directions and grows linearly in $E$ in the longitudinal direction. With a further increase in the energy a mode of correlated behavior of the partons is established, which stops the longitudinal growth. Simultaneously, the expansion in the transverse directions changes to $\ln \!E$, and a hollow mostly free of partons is formed inside the nucleons along the central axis in the direction of their motion. Numerical estimates of the corresponding parameters are obtained.