Investigating a doubly bottomed tetraquark with lattice QCD

Tetraquarks, states composed of four valence quarks, have been predicted to exist in quantum chromodynamics (QCD) since its inception. Using lattice QCD, a regularization of QCD on a finite-volume space-time grid, we investigate the spectrum of the doubly bottom four-quark system with isospin 0 and $J^P=1^+$. We construct a correlation matrix of local four-quark and non-local two-meson interpolating fields and determine the finite volume spectrum from its euclidean time evolution. A chiral extrapolation performed on five different gauge ensembles results in a $\bar{b}\bar{b}ud$ tetraquark mass of $(10476\pm24\pm10)$ MeV.