# Basics of doubly heavy tetraquarks

## TL;DR

This paper reviews the stability of doubly heavy tetraquarks, analyzing four-body dynamics, color-mixing, and spin effects, concluding stability for certain configurations like $bbar uar d$ but instability for all-heavy tetraquarks.

## Contribution

It provides a detailed analysis of the stability conditions of doubly heavy tetraquarks considering color and spin effects, with implications for all-heavy tetraquark states.

## Key findings

- Stability is favored when $M_Q/m_q o ext{large}$.
- The $bbar uar d$ tetraquark is predicted to be stable.
- All-heavy tetraquarks are generally unstable.

## Abstract

We outline the most important results regarding the stability of doubly heavy tetraquarks $QQ\bar q\bar q$ with an adequate treatment of the four-body dynamics. We consider both color-mixing and spin-dependent effects. Our results are straightforwardly applied to the case of all-heavy tetraquarks $QQ\bar Q\bar Q$. We conclude that the stability is favored in the limit $M_Q/m_q \gg 1$ pointing to the stability of the $bb\bar u\bar d$ state and the instability of all-heavy tetraquarks.