Soft Walls in Dynamic AdS/QCD and the Techni-dilaton

TL;DR

This paper explores soft wall behavior in a dynamic AdS/QCD model, showing how IR quark mass behavior influences meson spectra and the potential for a large techni-dilaton mass in walking gauge theories.

Contribution

It introduces a soft wall implementation in dynamic AdS/QCD that affects meson spectra and chiral symmetry breaking, highlighting the impact on techni-dilaton mass predictions.

Findings

Soft wall behavior leads to Regge-like meson trajectories.

IR quark mass decay significantly influences meson spectrum.

Breaking conformal symmetry can produce a heavy techni-dilaton.

Abstract

Dynamic AdS/QCD is a modification of AdS/QCD that includes the running of the anomalous dimension of the q-bar q quark bilinear and in which the generation of the constituent quark mass plays the role of an IR wall. The model allows one to move away smoothly from the controlled spectrum of the N=2 super Yang-Mills theory of the D3/probe-D7 system to more QCD-like theories with chiral symmetry breaking. We investigate soft wall behaviour in the model that gives Regge trajectories with M_{n,s}^2 ~ n,s. To achieve these behaviours requires the quark's constituent mass to fall peculiarly sharply in the IR so that meson physics is sensitive to RG scales well below the quark's on-shell mass. Including soft wall behaviour in models of walking gauge dynamics breaks the near conformal symmetry which is present above the quark on-shell mass which can generate a large mass for the techni-dilaton like state. We conclude that the meson spectrum is rather sensitive to the IR decoupling.