Glueball Decay Rates in the Witten-Sakai-Sugimoto Model

TL;DR

This paper revisits and extends calculations of glueball decay rates within the holographic Witten-Sakai-Sugimoto model, providing detailed decay patterns and mass estimates that compare to experimental candidates like f0(1500) and f0(1710).

Contribution

It offers new quantitative decay rate calculations for various glueball modes and identifies the most plausible scalar glueball candidate within the holographic framework.

Findings

The lowest exotic glueball has a lower mass and larger width than known candidates.

The nonexotic dilatonic scalar mode aligns with the properties of f0(1500) or f0(1710).

Tensor glueball decay pattern suggests a broad width above 2 GeV.

Abstract

We revisit and extend previous calculations of glueball decay rates in the Sakai-Sugimoto model, a holographic top-down approach for QCD with chiral quarks based on D8 probe branes in Witten's holographic model of nonsupersymmetric Yang-Mills theory. The rates for decays into two pions, two vector mesons, four pions, and the strongly suppressed decay into four pi0 are worked out quantitatively, using a range of the 't Hooft coupling which closely reproduces the decay rate of rho and omega mesons and also leads to a gluon condensate consistent with QCD sum rule calculations. The lowest holographic glueball, which arises from a rather exotic polarization of gravitons in the supergravity background, turns out to have a significantly lower mass and larger width than the two widely discussed glueball candidates f0(1500) and f0(1710). The lowest nonexotic and predominantly dilatonic scalar mode, which has a mass of 1487 MeV in the Witten-Sakai-Sugimoto model, instead provides a narrow glueball state, and we conjecture that only this nonexotic mode should be identified with a scalar glueball component of f0(1500) or f0(1710). Moreover the decay pattern of the tensor glueball is determined, which is found to have a comparatively broad total width when its mass is adjusted to around or above 2 GeV.