The total cross section of the reaction pp→ppK+K− has been determined
for proton--proton reactions with pbeam=3.67GeV/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.Comment: 12 pages, 3 figures Phys. Lett. B in prin