Holographic spectral functions of exotic spin-1 mesons

Abstract

We develop a general holographic framework for computing thermal spectral functions of exotic spin--1 mesons. A bulk Proca mass encodes the canonical ultraviolet dimension of the interpolating operator, allowing channels with different ultraviolet scaling to be treated within a unified membrane-flow formalism in the zero-spatial-momentum limit. We test this framework in a soft-wall model with a gluon-condensate background for the hybrid $\pi_1$ and tetraquark-like $Z_c$ channels. The results show that dissociation temperatures of both channels lie below the phase transition temperatures. Increasing $c$ delays dissociation in both channels, but through different effects: both the vacuum-mass shift and thermal spectral deformation contribute in the $\pi_1$ channel, whereas the latter dominates in the $Z_c$ channel. Nevertheless, for the same environment, the $Z_c$ resonance dissociates at a lower temperature than the $\pi_1$ resonance.