pp low energy parameters from annihilation cross section data

The recent experimental data obtained by the OBELIX group on total pp annihilation cross section are analysed; the low energy spin averaged parameters of the pp scattering amplitude (the imaginary parts of the S-wave scattering length and P-wave scattering volume) are extracted from the data. Their values are found to be equal to Im asc = −0.69 ± 0.01 (stat) ± 0.03 (sys) fm, Im Asc = −0.76 ± 0.05 (stat) ± 0.04 (sys) fm3. The results are in very good agreement with existing atomic data.