Production of Lambda Lambda and (Lambda n)over-bar in central Pb plus Pb collisions at root sNN=2.76 TeV within a covariant coalescence model

摘要

We study the production of Lambda Lambda and (Lambda n) over bar exotic states in central Pb + Pb collisions at root sNN = 2.76 TeV at the CERNLarge Hadron Collider (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 freeze-out. 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 (Lambda n) over bar, 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 (Lambda n) over bar via hadron coalescence. Our results suggest that the current experimental measurement at the 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.