More on heavy tetraquarks in lattice QCD at almost physical pion mass

TL;DR

This paper advances lattice QCD studies of heavy tetraquark states with various heavy quark combinations, analyzing their binding energies and state identification near physical pion masses using improved operator bases.

Contribution

It extends previous lattice QCD analyses to include heavier than bottom quarks and non-degenerate heavy quark pairs, employing a larger operator basis and a 3x3 GEVP for clearer state identification.

Findings

Dependence of binding energy on heavy quark mass studied.

Identification of potential bound states in $udar car b$ channel.

Initial results on $c c$ tetraquark system with expanded operator basis.

Abstract

We report on our progress in studying exotic, heavy tetraquark states, $qq\prime \bar Q\bar Q\prime$. Using publicly available dynamical $n_f =2+1$ Wilson-Clover gauge configurations, generated by the PACS-CS collaboration, with pion masses $\simeq$164, 299 and 415 MeV, we extend our previous analysis to heavy quark components containing heavier than physical bottom quarks $\bar Q\bar Q\prime=\bar b\prime\bar b\prime$ or $\bar Q\bar Q\prime=\bar b\bar b\prime$, charm and bottom quarks $\bar c\bar b$ and also only charm quarks $\bar c\bar c$. Throughout we employ NRQCD and relativistic heavy quarks for the heavier than bottom, bottom and charm quarks. Using our previously established diquark-antidiquark and meson-meson operator basis we comment in particular on the dependence of the binding energy on the mass of the heavy quark component $\bar Q\bar Q$, with heavy quarks ranging from $m_Q=0.85\ldots 6.3\cdot m_b$. In the heavy flavor non-degenerate case, $\bar Q\bar Q\prime$, and especially for the tetraquark channel $ud\bar c\bar b$, we extend our work to utilize a $3\times 3$ GEVP to study the ground and threshold states thereby enabling a clear identification of possible binding. Finally, we present initial work on the $\bar Q\bar Q\prime=\bar c\bar c$ system where a much larger operator basis is available in comparison to flavor combinations with NRQCD quarks.