Lattice Prediction for Deeply Bound Doubly Heavy Tetraquarks

Abstract

We investigate the possibility of $q{q}^{\prime }\bar{b}\bar{b}$ tetraquark bound states using $n_f=2+1$ lattice QCD ensembles with pion masses $\simeq 164$, $299$, and $415$ MeV. Motivated by observations from heavy baryon phenomenology, we consider two lattice interpolating operators both of which are expected to couple efficiently to tetraquark states: one with diquark-antidiquark and one with a meson-meson structure. Using nonrelativistic QCD to simulate the bottom quarks, we study the $ud\bar{b}\bar{b}$, $\ell s\bar{b}\bar{b}$ channels with $\ell =u,d$, and find unambiguous signals for strong-interaction-stable $J^P=1^{+}$ tetraquarks. These states are found to lie $189(10)$ and $98(7)$ MeV below the corresponding free two-meson thresholds.

5 pages, 3 figures; published version