Masses of Doubly Heavy Tetraquarks with Error Bars

TL;DR

This paper predicts the masses of doubly heavy tetraquarks using heavy-quark symmetry and experimental/lattice data, identifying stable states with respect to strong decays.

Contribution

It introduces a method to estimate doubly heavy tetraquark masses with error bars based on heavy-quark--diquark symmetry and existing experimental and lattice QCD data.

Findings

Predicted stable $bb$ tetraquarks with specific light flavors.

Mass predictions include error estimates.

Only certain doubly heavy tetraquarks are stable against strong decay.

Abstract

In the heavy-quark limit, the two heavy quarks in a doubly heavy baryon or a doubly heavy tetraquark are bound by their color-Coulomb potential into a compact diquark. The doubly heavy hadrons are related by the approximate heavy-quark--diquark symmetry of QCD to the heavy hadrons obtained by replacing the heavy diquark by a heavy antiquark. Effective field theories can be used to expand the masses of singly heavy hadrons and doubly heavy hadrons in inverse powers of the heavy quark masses. The coefficients in the expansions for doubly heavy tetraquarks can be determined from those for heavy mesons, heavy baryons, and doubly heavy baryons using heavy-quark--diquark symmetry. We predict the masses of the ground-state doubly heavy tetraquarks with error bars using as inputs the masses of heavy mesons and heavy baryons measured in experiments and the masses of doubly heavy baryons calculated using lattice QCD. The only doubly heavy tetraquarks predicted to be stable with respect to strong decays are $bb$ tetraquarks with light flavor $\bar u \bar d$, $\bar s \bar u$ and $\bar s \bar d$.