# Lattice QCD investigation of a doubly-bottom $\bar{b} \bar{b} u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$

## TL;DR

This study uses lattice QCD with multiple ensembles and advanced analysis to confirm a stable doubly-bottom tetraquark state with specific quantum numbers, providing detailed mass and binding energy estimates.

## Contribution

It introduces a comprehensive lattice QCD approach including nonlocal interpolators and Lüscher analysis to study the doubly-bottom tetraquark, improving upon previous methods.

## Key findings

- Identifies a stable $ar{b} ar{b} u d$ tetraquark with a binding energy of about -128 MeV.
- Provides a mass estimate of approximately 10476 MeV for the tetraquark.
- Confirms the tetraquark's stability against strong and electromagnetic decays.

## Abstract

We use lattice QCD to investigate the spectrum of the $\bar{b} \bar{b} u d$ four-quark system with quantum numbers $I(J^P) = 0(1^+)$. We use five different gauge-link ensembles with $2+1$ flavors of domain-wall fermions, including one at the physical pion mass, and treat the heavy $\bar{b}$ quark within the framework of lattice nonrelativistic QCD. Our work improves upon previous similar computations by considering in addition to local four-quark interpolators also nonlocal two-meson interpolators and by performing a L\"uscher analysis to extrapolate our results to infinite volume. We obtain a binding energy of $(-128 \pm 24 \pm 10) \, \textrm{MeV}$, corresponding to the mass $(10476 \pm 24 \pm 10) \, \textrm{MeV}$, which confirms the existence of a $\bar{b} \bar{b} u d$ tetraquark that is stable with respect to the strong and electromagnetic interactions.