Universal Curve for pi pi Scattering Lengths by Optimal Extrapolation Techniques

Using the method of optimal extrapolation to interior points, we re-evaluate the equation of the universal curve of the ππs-wave scattering lengths. We reproduce the gross features of previous determinations, but with a realistic error, without any detailed assumption on the asymptotic behaviour. Possible implications of our result on the numerical value of thep-wave scattering length are qualitatively discussed.