Coherent production of multimeson final states on A ∼ 20 nuclei by K − of 5.5, 10.0, 12.7 GeV

Abstract

Coherent production of Kπ, K2π and K3π final states from A ∼ 20 nuclei by K − beams of 5.5, 10.0 and 12.7 GeV is analyzed. Final states with ⩽ 2 π O are included. Coherent Kπ production occurs (although forbidden via 0 + exchange) and is dominated by the K ∗ (890). The shape of the t distribution, the alignment of the produced meson and the ratio of the cross section on nuclei to that on hydrogen are consistent with optical model predictions assuming that K ∗ (890) are produced on single nucleons by exchange of isoscalar trajectories of natural parity ( J P = 1 −, 2 +, etc.) and that the K ∗ (890) absorption in nuclear matter equals that of the K −. Coherent Kππ production (allowed via 0 +, 1 −, 2 +, etc. exchange) is dominated by the Q phenomenon. A Dalitz plot and angular correlation analysis yields values for Kϱ/ K ∗π fractions, and shows that J P = 1 + S-wave K ∗π dominates the coherently produced Q. The helicity of the Q is found to be compatible with 0. The Q − -nucleaon total cross section is estimated to be 0.98 −0.37 +024 times the K − -nucleon total cross section from a comparison of the coherent Q-production cross section with corresponding hydrogen cross sections at 10 and 12.7 GeV. We observe coherent production of K ω. The ration Kω/ Kππ coherently produced in the Q mass region is (4 ± 1)%. Coherent production of K −π +π − and K O π +π − π O is observed in the L region. Coherent production is not observed in the K4 π channels.