In recent years, the strangeness production reactions in NN collisions have attracted a considerable amount of interest. These reactions are expected to provide valuable information on the manifestation of Quantum chromodynamics (QCD) in the nonperturbative region. For example, the φ meson is expected to probe the admixture of strange quark pairs in the nucleon wave function. The near-threshold reactions are expected to provide valuable information about the meson-meson, meson-baryon,
and hyperon-nucleon interactions.
We report the differential and total cross sections for the pp → ppKK/φ reaction at Tp= 2.567 (below the φ meson threshold) and 2.83 GeV (above the φ meson threshold). We use detailed model descriptions to fit a variety of one dimensional distributions in order to separate the pp → ppφ cross section from that of non- φ production. The differential spectra show that higher partial waves represent the majority of the pp → pp φ total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave φp enhancement near threshold. On the other hand, strong preferences to the low Kp and Kpp invariant masses are observed in non- kaon pair productions. The cusp effect in the KK distribution at the K0 K0 threshold is clear and some evidence is also found for coupling between the Kp and K0n channels. Beside of the mentioned reactions, we also show the preliminary results for the search for a possible Kpp bound state in the pp → pKΛ reaction at Tp=2.567 GeV.
