Collective String Interactions in AdS/QCD and High-Multiplicity pA Collisions

TL;DR

This paper explores the interaction and collective behavior of QCD strings in high-energy collisions using AdS/QCD models, revealing insights into string mixing, gluonic cores, and conditions leading to quark-gluon plasma formation.

Contribution

It introduces a holographic approach to study QCD string interactions, including scalar sector analysis, string collectivization, and dynamical simulations of multi-string systems.

Findings

Identification of glueballs and scalar mesons and their mixing

Holographic images of QCD strings have gluonic cores and sigma clouds

Conditions for string collectivization into a QGP fireball

Abstract

QCD strings originate from high-energy scattering in the form of Reggeons and Pomerons, and have been studied in some detail in lattice numerical simulations. Production of multiple strings, with their subsequent breaking, is now a mainstream model of high energy $pp$ and $pA$ collisions. Recent LHC experiments revealed that high multiplicity end of such collisions show interesting collective effects. This ignited an interest in the interaction of QCD strings and multi-string dynamics. Holographic models, collectively known as AdS/QCD, developed in the last decade, describe both hadronic spectroscopy and basic thermodynamics, but so far no studies of the QCD strings have been done in this context. The subject of this paper is to do this. First, we study in more detail the scalar sector of hadronic spectroscopy, identifying "glueballs" and "scalar mesons," and calculate the degree of their mixing. The QCD strings, holographic images of the fundamental strings, thus have a "gluonic core" and a "sigma cloud." The latter generates $\sigma$ exchanges and collectivization of the strings, affecting, at a certain density, the chiral condensate and even the minimum of the effective string potential, responsible for the very existence of the QCD strings. Finally, we run dynamical simulations of the multi-string systems, in the "spaghetti" setting approximating central $pA$ collisions, and specify conditions for their collectivization into a black hole, or the dual QGP fireball.