Correlation function of \spipi pairs in the third (0.50--0.70 \GeVc) \kt interval for $N_{\mathrm{ch}}>~30$, the fits are performed using CATS~ employing the RSM. The left (right) panel shows the results assuming a polynomial of first (second) degree as background. The statistical and systematic uncertainties are represented by the bars and rectangles, respectively. The uncertainty bands of the fit function are obtained by employing a bootstrap~ procedure.