Cross section of the $pp\to K^{+}{\Sigma }^{+}n$ reaction close to threshold

Abstract

We have measured inclusive data on $K^{+}$-meson production in $pp$ collisions at COSY Jülich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $\Lambda p$, ${\Sigma }^{0}p$ and ${\Sigma }^{+}n$. The cross section for the ${\Sigma }^{+}n$ channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

Comments: accepted by Phys. lett. B some typos corrected