Heavy Baryons and their Exotics from Instantons in Holographic QCD

Abstract

We use a variant of the $D4$-$D8$ construction that includes two chiral and one heavy meson, to describe heavy-light baryons and their exotics as heavy mesons bound to a flavor instanton in bulk. At strong coupling, the heavy meson is shown to {\it always bind} in the form of a flavor instanton zero mode in the fundamental representation. The ensuing instanton moduli for the heavy baryons exhibits both chiral and heavy quark symmetry. We detail how to quantize it, and derive model independent mass relations for heavy bayons with a single-heavy quark in leading order, in overall agreement with the reported baryonic spectra with one charm or bottom. We also discuss the low-lying masses and quantum assignments for the even and odd parity states, some of which are yet to be observed. We extend our analysis to double-heavy pentaquarks with hidden charm and bottom. In leading order, we find a pair of doube-heavy iso-doublets with $IJ^\pi=\frac 12 {\frac 12}^-, \frac 12 {\frac 32}^-$ assignments for all heavy flavor combinations. We also find five new Delta-like pentaquark states with $IJ^\pi=\frac 32 {\frac 12}^-, \frac 32 {\frac 32}^-, \frac 32 {\frac 52}^-$ assignments for both charm and bottom.