# Exotic $bc\bar q\bar q$ four-quark states

## TL;DR

This study systematically investigates exotic four-quark states with heavy flavors, predicting stable isoscalar states with specific quantum numbers across various models, and finds isovector states unbound, with implications for experimental detection.

## Contribution

It provides a robust, model-independent prediction of the quantum numbers and stability of heavy-flavor exotic tetraquarks, especially the isoscalar $J^P=0^+$ and $J^P=1^+$ states.

## Key findings

- Predicted isoscalar $J^P=0^+$ state is stable against strong and electromagnetic decays.
- Predicted isoscalar $J^P=1^+$ state decays electromagnetically to $ar B D \gamma$.
- Isovector states are unbound, ruling out charged partners.

## Abstract

We carry out a systematic study of exotic $QQ^\prime \bar q\bar q$ four-quark states containing distinguishable heavy flavors, $b$ and $c$. Different generic constituent models are explored in an attempt to extract general conclusions. The results are robust, predicting the same sets of quantum numbers as the best candidates to lodge bound states independently of the model used, the isoscalar $J^P=0^+$ and $J^P=1^+$ states. The first state would be strong and electromagnetic-interaction stable while the second would decay electromagnetically to $\bar B D \gamma$. Isovector states are found to be unbound, preventing the existence of charged partners. The interest on exotic heavy-light tetraquarks with non identical heavy-flavors comes reinforced by the recent estimation of the production rate of the isoscalar $bc\bar u \bar d$ $J^P=1^+$ state, two orders of magnitude larger than that of the $bb\bar u\bar d$ analogous state.