Holographic Pomeron and the Schwinger Mechanism

Abstract

I revisit the problem of dipole-dipole scattering via exchanges of soft Pomerons in the context of holographic QCD with confinement and show that a single closed string exchange contribution to the eikonalized dipole-dipole scattering amplitude yields a Regge behavior of the elastic amplitude. I provide a physical interpretation of the semi-classical worldsheets driving the Regge behavior for (−t) > 0 in terms of worldsheet instantons which describe the Schwinger mechanism for string pair creation by an effective electric field induced by the relative rapidity χ of the scattering dipoles. The analysis naturally explains the diffusion in the impact parameter space encoded in the Pomeron exchange via the Unruh temperature of accelerated strings under the electric field. I 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, I show that the total dipole-dipole cross section obeys the Froissart unitarity bound.