K − meson production in the proton–proton reaction at 3.67 GeV/ c

The total cross section of the reaction pp→ ppK + K − has been determined for proton–proton reactions with p beam =3.67 GeV/c . This represents the first cross section measurement of the pp→ ppK − K + channel near threshold, and is equivalent to the inclusive pp→ ppK − X cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive pp→ ppK + X meson production at the same CM energy above the corresponding threshold. This large difference in the K + and K − meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.