A broad pseudovector glueball from holographic QCD

TL;DR

This paper investigates the decay properties of a pseudovector glueball in holographic QCD, predicting it to be an extremely broad resonance when extrapolated to real-world parameters.

Contribution

It provides a holographic QCD calculation of the decay width of the lightest pseudovector glueball, including dominant decay channels and coupling mechanisms.

Findings

Predicted decay width is very broad for realistic parameters.

Dominant decay channels are determined by a Chern-Simons-like action.

Couplings from the Dirac-Born-Infeld action are subdominant.

Abstract

We study the decay of a pseudovector glueball with quantum numbers $J^{PC}=1^{+-}$, the lightest glueball with spin different from zero or two, in the top-down holographic Witten-Sakai-Sugimoto model. This glueball is dual to the string-theoretic Kalb-Ramond tensor field, which completely fixes all its couplings by gauge invariance and $D$-brane anomaly inflow. The dominant decay channels are determined by a Chern-Simons-like action for the flavor branes; couplings from the Dirac-Born-Infeld action turn out to be subdominant. While the resulting width is parametrically of order $N_c^{-2}\lambda^{-1}$ for $N_c$ colors and 't Hooft coupling $\lambda$, when extrapolated to $N_c=3$ and with $\lambda$ matched to experimental data, the prediction is that the pseudovector glueball is an extremely broad resonance.