AdS/QCD Modified Soft Wall Model and Light Meson Spectra

TL;DR

This paper introduces a modified soft wall AdS/QCD model with a UV cutoff to better fit light meson spectra, revealing limitations in modeling certain scalar resonances like the $f_{0}(500)$.

Contribution

The study proposes a novel AdS/QCD soft wall model with a UV cutoff, providing improved meson mass fits and insights into scalar resonance modeling.

Findings

Scalar and vector meson masses fit within 7.64% RMS error.

Model parameters include UV cutoff position and dilaton slope.

The $f_{0}(500)$ resonance cannot be modeled as a $q\overline{q}$ state.

Abstract

We analyze here the mass spectrum of light vector and scalar mesons applying a novel approach where a modified soft wall model that includes a UV-cutoff at a finite $z$-position in the AdS space is used, thus introducing an extra energy scale. For this model, we found that the masses for the scalar and vector spectra are well fitted within $\delta_{RMS}=7.64\%$ for these states, with non-linear trajectories given by two common parameters, the UV locus $z_{0}$ and the quadratic dilaton profile slope $\kappa$. We also conclude that in this model, the $f_{0}(500)$ scalar resonance cannot be fitted holographycally as a $q\overline{q}$ state since we cannot find a trajectory that include this pole. This result is in agreement with the most recent phenomenological and theoretical methods.