We report the first lattice quantum chromodynamics (QCD) study of deuteron($np$)-like dibaryons with heavy quark flavours. These include particles with following dibaryon structures and valence quark contents: $Sigma_cXi_{cc} (uucucc)$, $Omega_cOmega_{cc} (sscscc)$, $Sigma_bXi_{bb} (uububb)$, $Omega_bOmega_{bb} (ssbsbb)$ and $Omega_{ccb}Omega_{cbb} (ccbcbb)$, and with spin ($J$)-parity ($P$), $J^{P} equiv 1^{+}$. Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons $Omega_cOmega_{cc} (sscscc)$, $Omega_bOmega_{bb} (ssbsbb)$ and $Omega_{ccb}Omega_{cbb} (ccbcbb)$ are below their respective two-baryon thresholds, suggesting the presence of bound states which are stable under strong and electromagnetic interactions. We also predict their masses precisely. For dibaryons $Sigma_cXi_{cc} (uucucc)$, and $Sigma_bXi_{bb} (uububb)$, we could not reach to a definitive conclusion about the presence of any bound state due to large systematics associated with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the Periodic Table.
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