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

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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 fm < a₀ < 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 Σ⁰, 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 Σ⁰/Λ ratio, while the positive scattering length could be favored when we regard λ as a free fitting parameter.