$\pi \pi$ scattering S wave from the data on the reaction ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$

The results of the recent experiments on the reaction ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 $\pi \pi$ S wave phase shift ${\delta }_0^0$ and inelasticity ${\eta }_0^0$ a new set of data is obtained. Difficulties emerging when using the physical solutions for the ${\pi }^0{\pi }^0$ S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the ${\pi }^0{\pi }^0$ invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the $f_0(980)$ resonance thorough experimental investigations of the reaction ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ in the m region near the $K\bar{K}$ threshold are required.