Heavy-quark symmetry implies stable heavy tetraquark mesons $Q_iQ_j \bar q_k \bar q_l$

TL;DR

Heavy-quark symmetry predicts the existence of stable doubly heavy tetraquark mesons, with double-beauty states likely stable against strong decays, offering new insights into hadron structure and the role of diquarks.

Contribution

This paper predicts the stability of certain doubly heavy tetraquark states using heavy-quark symmetry and finite-mass corrections, highlighting potential experimental signatures.

Findings

Double-beauty tetraquarks $bbar u ar d$, $bbar u ar s$, $bbar d ar s$ are stable against strong decays.

Double-charm and mixed states are unstable and will decay into heavy-light mesons.

Observation of double-beauty states would confirm tetraquark existence and the importance of diquarks.

Abstract

For very heavy quarks $Q$, relations derived from heavy-quark symmetry predict the existence of novel narrow doubly heavy tetraquark states of the form $Q_iQ_j \bar q_k \bar q_l$ (subscripts label flavors), where $q$ designates a light quark. By evaluating finite-mass corrections, we predict that double-beauty states composed of $bb\bar u \bar d$, $bb\bar u \bar s$, and $bb\bar d \bar s$ will be stable against strong decays, whereas the double-charm states $cc \bar q_k \bar q_l$, mixed beauty+charm states $bc \bar q_k \bar q_l$, and heavier $bb \bar q_k \bar q_l$ states will dissociate into pairs of heavy-light mesons. Observation of a new double-beauty state through its weak decays would establish the existence of tetraquarks and illuminate the role of heavy color-antitriplet diquarks as hadron constituents.