An Eta Primer: Solving the U(1) Problem with AdS/QCD

TL;DR

This paper uses a holographic QCD model inspired by AdS/CFT to calculate eta and eta prime meson properties, achieving results consistent with experimental data.

Contribution

It introduces a minimal AdS/QCD model that accurately predicts pseudoscalar meson masses and decay rates with few free parameters.

Findings

Eta and eta prime masses match experimental values

Decay rates into photons agree with data

Model has strong predictive power with minimal assumptions

Abstract

Inspired by the AdS/CFT correspondence, we study the pseudoscalar mesons of QCD through a dual embedding in a strongly curved extra dimensional spacetime. This model incorporates the consequences of symmetry and has very few free parameters, due to constraints from five-dimensions and the operator product expansion of QCD. Using as inputs the pion, kaon, and rho masses and fpi, we compute the eta and eta prime masses to be 520 and 867 MeV, respectively. Their decay rates into photons are also computed and found to be in good agreement with data.