pi pi --> pi pi cross-sections near threshold

An analysis of new data for the reaction p6p!p6p1n at incident energies between 223 and 284 MeV is presented. p1p2 cross sections are obtained via Goebel-Chew-Low techniques by extrapolation to the pion pole using the pseudoperipheral approximation. A consistency check between the present experimental results and previous experiments at higher energies is made using Roy equations. The isospin 0, S-wave pp scattering length was obtained using a variety of methods. The result obtained from a threshold expansion is a0 0 50.20460.014 ~statistical! 60.008 ~systematic! in inverse pion mass units. It is shown that there are significant differences between the reaction mechanisms for the (p2p1) and (p1p1) channels