Enhanced production of ΛΛ pairs near threshold in the (K-,K+) reaction on 12C

Enhanced production of ΛΛ pairs, above the prediction of a two-step process model, is observed near threshold (around the masses of 2.23 – 2.26 GeV/c2) in the12C(K−,K+) reaction at PK− = 1.66GeV/c using a scintillating fiber target. The differential cross section for the ΛΛ production averaged over 2.3° ≤ $$K + ≤ 14.7° in the momentum region 0.95 ≤ pK + ≤ 1.3GeV/c was found to be 7.6 ± 1.3 μb/sr, and that for the enhancement approximately 3 μb/sr.