  The production of the Sigma+ hyperon through the pp->K+nSigma+ reaction has
been investigated at four energies close to threshold, 1.826, 1.920, 1.958, and
2.020 GeV. At low energies, correlated K+pi+ pairs can only originate from
Sigma+ production so that their measurement allows the total cross section for
the reaction to be determined. The results obtained are completely consistent
with the values extracted from the study of the K+-proton correlation spectra
obtained in the same experiment. These spectra, as well as the inclusive K+
momentum distributions, also provide conservative upper limits on the Sigma+
production rates. The measurements show a Sigma+ production cross section that
varies roughly like phase space and, in particular, none of the three
experimental approaches used supports the anomalously high near-threshold
pp->K+ nSigma+ total cross section previously reported [T. Rozek et al., Phys.
Lett. B 643, 251 (2006)].

High Energy Physics - Experiment;Nuclear Experiment;Nuclear Theory