Eikonal but not: a complementary view of high energy evolution

TL;DR

This paper presents a novel interpretation of high energy evolution equations in QCD, shifting from wave function evolution to S-matrix evolution, leading to non-eikonal scattering and gluon radiation.

Contribution

It introduces a new perspective on high energy evolution, interpreting it as an evolution of the S-matrix rather than the hadronic wave function, akin to the Heisenberg picture.

Findings

Evolution acts on the S-matrix, not the wave function.

Scattering becomes non-eikonal with additional boosts.

Enhanced gluon radiation in the final state.

Abstract

The high energy evolution equations that describe the evolution of hadronic amplitudes with energy are derived assuming eikonal interaction of the evolved hadronic wave function with the target. In this note we remark that this derivation allows a different interpretation, whereby the hadronic wave function is not evolved, but instead the evolution acts on the S - matrix operator. In this approach, analogous to the Heisenberg picture of Quantum mechanics, the scattering is not eikonal and additional boost provides for radiation of more gluons in the final state.