Hadron spectroscopy using the light-front holographic Schrödinger Equation and the 't Hooft Equation

Light-front holographic QCD provides a successful first approximation to hadron spectroscopy in the chiral limit of ($3+1$)-dim light-front QCD, where a holographic Schr\"odinger-like equation, with an emerging confining scale, $\ensuremath{\kappa}$, governs confinement in the transverse direction. In its supersymmetric formulation, light-front holography predicts that each baryon has two superpartners: a meson and a tetraquark, with their degenerate masses being generated by the same scale, $\ensuremath{\kappa}$. In nature, this mass degeneracy is lifted by chiral symmetry breaking and longitudinal confinement. In this paper, we show that the latter can be successfully captured by the 't Hooft equation of ($1+1$)-dim, large ${N}_{c}$, QCD. Together, the holographic Schr\"odinger equation and the 't Hooft equation provide a good global description of the data across the full hadron spectrum with a universal $\ensuremath{\kappa}$.