Production of $\Lambda\Lambda$ and $\bar{\Lambda \text{n}}$ in central Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV within a covariant coalescence model

We study the production of $\Lambda\Lambda$ and $\overline{\Lambda \text{n}}$ exotic states in central Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at LHC via both hadron and quark coalescence within a covariant coalescence model with a blast-wave-like parametrization for the phase-space configurations of constituent particles at freezeout. In the hadron coalescence, the two states are considered as molecular states while they are considered as six-quark states in the quark coalescence.For $\overline{\Lambda \text{n}}$, we find that the yields of both molecular and six-quark states are much larger than the experimental upper-limits. For $\Lambda\Lambda$, while the molecule-state yield is much larger than the experimental upper-limits, the six-quark-state yield could be lower than the upper-limits. The higher molecule-state yields are mainly due to the large contribution of short-lived strong resonance decays into (anti-)nucleons and (anti-)$\Lambda$ which can significantly enhance the molecule-state yields of $\Lambda\Lambda$ and $\overline{\Lambda \text{n}}$ via hadron coalescence. Our results suggest that the current experimental measurement at LHC cannot exclude the existence of the $\Lambda\Lambda$ as an exotic six-quark state, and if $\Lambda\Lambda$ is a six-quark state, it is then on the brink of being discovered.