Light scalar tetraquarks from a holographic perspective

TL;DR

This paper explores how light scalar tetraquarks can be modeled within holographic QCD, showing that strong binding effects and anomalous dimensions can produce lighter tetraquark states and explaining their potential to dissolve into the continuum.

Contribution

It introduces a holographic mechanism for the emergence of light scalar tetraquarks via bulk-mass corrections linked to anomalous dimensions in AdS/QCD models.

Findings

Holographic encoding of strong tetraquark binding through bulk-mass corrections.

A lower bound on tetraquark masses derived from the model.

Higher tetraquark excitations tend to be heavier and may dissolve into the continuum.

Abstract

We discuss how a dominant tetraquark component of the lightest scalar mesons may emerge in AdS/QCD gravity duals. In particular, we show that the exceptionally strong binding required to render the tetraquark ground state lighter than the lowest-lying scalar quark-antiquark nonet can be holographically encoded into bulk-mass corrections for the tetraquark's dual mode. The latter are argued to originate from the anomalous dimension of the corresponding four-quark interpolator. To provide a concrete example, we implement this mechanism into the dilaton soft-wall dual for holographic QCD. Preventing the lowest-lying dual mode from collapsing into the AdS boundary then establishes a rather generic lower bound on the tetraquark mass (which may be overcome in the presence of additional background fields). We further demonstrate that the higher tetraquark excitations can become heavier than their quark-antiquark counterparts and are thus likely to dissolve into the multiparticle continuum.