Holographic glueball structure

TL;DR

This paper analyzes scalar glueball correlation functions using holographic QCD models, deriving estimates for gluon condensates, instanton distributions, and glueball decay constants, and compares the hard-wall and soft-wall approaches.

Contribution

It provides a systematic holographic analysis of glueball correlators, linking them to QCD operator product expansion and offering new estimates for gluon condensates and decay constants.

Findings

Hard-wall model encodes more relevant QCD physics.

Predicted glueball decay constant f ~ 0.8-0.9 GeV matches QCD sum rule and lattice results.

Holographic correlators reveal complementarity between nonperturbative effects.

Abstract

We derive and systematically analyze scalar glueball correlation functions in both the hard-wall and dilaton soft-wall approximations to holographic QCD. The dynamical content of the holographic correlators is uncovered by examining their spectral density and by relating them to the operator product expansion, a dilatational low-energy theorem and a recently suggested two-dimensional power correction associated with the short-distance behavior of the heavy-quark potential. This approach provides holographic estimates for the three lowest-dimensional gluon condensates or alternatively their Wilson coefficients, the two leading moments of the instanton size distribution in the QCD vacuum and an effective UV gluon mass. A remarkable complementarity between the nonperturbative physics of the hard- and soft-wall correlators emerges, and their ability to describe detailed QCD results can be assessed quantitatively. We further provide the first holographic estimates for the decay constants of the 0++ glueball and its excitations. The hard-wall background turns out to encode more of the relevant QCD physics, and its prediction f ~ 0.8-0.9 GeV for the phenomenologically important ground state decay constant agrees inside errors with recent QCD sum rule and lattice results.