Spectrum of two-flavored spin-zero heavy dibaryons in lattice QCD

We present the ground state energy spectra of two-flavored heavy dibaryons in the spin-singlet channel. In particular, the ground state masses of $\Omega_{llQ}\Omega_{llQ}, \Omega_{QlQ}\Omega_{llQ}$ and $\Omega_{QlQ}\Omega_{QlQ}$ states are computed and compared with their respective lowest non-interacting energy levels, where the flavor $Q \in (c,b)$ denotes charm and bottom quarks, and the other flavor $l \in {s,c,b}$ represents strange, charm and bottom, respectively. Considering their valence quark structures, these hadrons could be thought of as the heavy flavor analogues of spin-singlet nucleon-nucleon states. The gauge configurations employed in this study are HISQ ensembles with $N_f = 2+1+1$ flavors, generated by the MILC collaboration, at four lattice spacings, namely $a=0.1207, 0.0888, 0.0582$ and $0.0448$ fm. The aforementioned states are also computed at different quark masses, between $m_s \le m_l \le m_b$, including at unphysical heavy quark masses, to explore the quark mass dependence of any possible binding. For the dibaryon states $\Omega_{bbc}\Omega_{bbc}, \Omega_{ccb}\Omega_{ccb}$ and $\Omega_{ccb} \Omega_{bbc}$, we find a clear evidence of an energy level below their respective non-interacting energy levels. In addition, for these dibaryons at quark masses $m_c < m_l \le m_b$, a trend is found where the gap, between the lowest energy levels and the respective lowest non-interacting levels, increases as the quark mass $m_l$ increases. We also study the heavy quark spin-symmetry and its breaking for these heavy dibaryons.