Holographic Pomeron and the Schwinger Mechanism

TL;DR

This paper explores holographic QCD to understand dipole-dipole scattering, revealing a Regge behavior linked to string pair creation via the Schwinger mechanism, and explains impact parameter diffusion through Unruh temperature effects.

Contribution

It introduces a novel interpretation of Pomeron exchange as string pair creation driven by an electric field, connecting holographic models with non-perturbative QCD phenomena.

Findings

Single string exchange yields Regge behavior with distinct slope and intercept.

Worldsheet instantons describe the Schwinger mechanism for string pair creation.

Total cross section obeys Froissart bound after summing multi-Pomeron exchanges.

Abstract

We revisit the problem of dipole-dipole scattering via exchanges of soft Pomerons in the context of holographic QCD. We show that a single closed string exchange contribution to the eikonalized dipole-dipole scattering amplitude yields a Regge behavior of the elastic amplitude; the corresponding slope and intercept are different from previous results obtained by a variational analysis of semi-classical surfaces. We provide a physical interpretation of the semi-classical worldsheets driving the Regge behavior for (-t)>0 in terms of worldsheet instantons. The latter describe the Schwinger mechanism for string pair creation by an electric field, where the longitudinal electric field E_L=\sigma_T tanh(\chi/2) at the origin of this non-perturbative mechanism is induced by the relative rapidity {\chi} of the scattering dipoles. Our analysis naturally explains the diffusion in the impact parameter space encoded in the Pomeron exchange; in our picture, it is due to the Unruh temperature of accelerated strings under the electric field. We also argue for the existence of a "micro-fireball" in the middle of the transverse space due to the soft Pomeron exchange, which may be at the origin of the thermal character of multiparticle production in ep/pp collisions. After summing over uncorrelated multi-Pomeron exchanges, we find that the total dipole-dipole cross section obeys the Froissart unitarity bound.