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

Abstract

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

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