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

Abstract

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.

Talk given at the 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015), Sendai, Japan, 7-12 Sep 2015, 8 pages, 7 figures