The pp→K+nΣ+ reaction near threshold

Inclusive K + production in proton–proton collisions has been measured at a beam energy of 2.16 GeV using the COSY-ANKE magnetic spectrometer. The resulting spectrum, as well as those corresponding to K + p and K + π + correlated pairs, can all be well described using consistent values of the total cross sections for the p p → K + p Λ , p p → K + p Σ 0 , and p p → K + n Σ + reactions. While the resulting values for Λ and Σ 0 production are in good agreement with world data, our value for the total Σ + production cross section, σ ( p p → K + n Σ + ) = ( 2.5 ± 0.6 stat ± 0.4 syst ) μb at an excess energy of e = 129 MeV , could only be reconciled with other recently published data if there were a highly unusual near threshold behaviour.