New measurements of the anti-pp annihilation cross section at very low energy

The pp total annihilation cross section has been measured at four values of the p incident momentum, between 70 MeV/c and 38 MeV/c, with the Obelix apparatus at LEAR. The new measurements are in agreement with the trend of previous measurements of the antip-p total annihilation cross section at low energy, performed by the Obelix experiment (A. Bertin et al., Phys. Lett. B 369(1996)77; A. Benedettini et al., Nucl. Phys. B Proc. Suppl..56A(1997)58), as well as with a fit of the latter data based on a low energy expansion of the scattering amplitude (J. Carbonell, K.V. Protasov, A. Zenoni, Phys. Lett. B 397(1997)345). The departure of the annihilation cross section from a smooth behaviour, suggested by a previous measurement of the cross section around 44 MeV/c (A. Bertin et al., Phys. Lett. B 369(1996)77), is not confirmed by the new data.