Measurements of the near threshold Lambda and Sigma0 production via the pp->pK+Lambda/Sigma0 reaction at COSY-11 have shown that the Lambda/Sigma0 cross section ratio exceeds the value at high excess energies Q >= 300 MeV by an order of magnitude. For a better understanding additional data have been taken between 13 MeV and 60 MeV excess energy. Within the first 20 MeV excess energy a strong decrease of the cross section ratio is observed, with a less steep decrease in the higher excess energy range. A description of the data with a parametrisation including p-Y final state interactions suggests a much smaller p-Sigma0 FSI compared to the p-Lambda system.
document in PDF format (~131kB)
AIP Conf.Proc. 717 (2004) 852-857