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Lambda-Lambda interaction from two-particle intensity correlation in relativistic heavy-ion collisions

We investigate $ΛΛ$ interaction dependence of the $ΛΛ$ intensity correlation in high-energy heavy-ion collisions. By analyzing the correlation data recently obtained by the STAR collaboration based on theoretically proposed $ΛΛ$ interactions, we give a constraint on the $ΛΛ$ scattering length, $-1.25~\text{fm} < a_0 < 0$, suggesting that $ΛΛ$ interaction is weakly attractive and there is no loosely bound state. In addition to the fermionic quantum statistics and the $ΛΛ$ interaction, effects of collective flow, feed-down from $Σ^0$, and the residual source are also found to be important to understand the data. We demonstrate that the correlation data favor negative $ΛΛ$ scattering length with the pair purity parameter $λ=(0.67)^2$ evaluated by using experimental data on the $Σ^0/Λ$ ratio, while the positive scattering length could be favored when we regard $λ$ as a free fitting parameter.