Tetraquark mass relations in quark and diquark models

We present new linear relations among the masses of S-wave tetraquarks with either one flavour (Q Q Q over bar Q over bar ) or two (Q Q q over bar q over bar ). Because the relations are sensitive to the hidden-colour, spin, and spatial degrees of freedom, comparison to experimental data can help to reveal the internal structure of tetraquarks, and discriminate among different theoretical models. Depending on the model, the relations are either exact, or valid in perturbation theory, and a thorough comparison with existing literature confirms their validity at the MeV level. Additionally, we explore the connections among tetraquark models, and show how those with effective (quark or diquark) masses are related to dynamical potential models. We also show how the spectrum of diquark models is effectively a limiting case of (more general) quark models, and in particular, that the diquark concept is most relevant in the particular combination Q Q q over bar q over bar , where Q is much heavier than q over bar . Crown Copyright (c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.

Automated summary

This article presents new linear relations among the masses of S-wave tetraquarks, which can help to reveal the internal structure of tetraquarks and discriminate among different theoretical models. The validity of these relations is confirmed through a thorough comparison with experimental data.