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

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 $m_Q=0.85\dots 6.3\cdot m_b$. 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.

8 pages, 5 figures, proceedings contribution to "Lattice 2017. 35th International Symposium on Lattice Field Theory", 18th-24th June 2017, Granada, Spain