$\mathrm{\Lambda }\mathrm{\Lambda }$ Correlation Function in $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$

We present $\mathrm{\Lambda }\mathrm{\Lambda }$ correlation measurements in heavy-ion collisions for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the $\mathrm{\Lambda }\mathrm{\Lambda }$ correlation function and interaction parameters for dihyperon searches are discussed.

Figure 1

The invariant mass distribution for $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ produced in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$, for 0–80% centrality. The $\mathrm{\Lambda }$ ($\overline{\mathrm{\Lambda }}$) candidates lying in the mass range 1.112 to $1.120\mathrm{GeV}/c^2$, shown by solid red vertical lines, were selected for the correlation measurement.

Figure 2

The $\mathrm{\Lambda }\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}\overline{\mathrm{\Lambda }}$ correlation function in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$, for 0–80% centrality. The plotted errors are statistical only.

Figure 3

The combined $\mathrm{\Lambda }\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}\overline{\mathrm{\Lambda }}$ correlation function for 0–80% centrality $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. Curves correspond to fits using the Lednický-Lyuboshitz (LL) analytical model with and without a residual correlation term [23]. The dotted line corresponds to quantum statistics with a source size of 3.13 fm. The shaded band corresponds to the systematic error.

Figure 4

The $\mathrm{\Lambda }\mathrm{\Lambda }$ interaction parameters from this experiment (solid circle), where the shaded band represents the systematic error. The interaction parameters from $pp$, $pn$ singlet ($s$), and triplet ($t$) states, and from $nn$, $p\mathrm{\Lambda }$ ($s$), and $p\mathrm{\Lambda }$ ($t$) states are shown as open markers [27]. Also, the $\mathrm{\Lambda }\mathrm{\Lambda }$ interaction parameters that reproduce the NAGARA event are shown as open stars [28, 29].