Experimental study of the pd-->3He K+K- and pd-->3He phi reactions close to threshold

摘要

Two-kaon production in proton-deuteron collisions has been studied at three energies close to threshold using a calibrated magnetic spectrograph to measure the final He-3 and a vertex detector to measure the K+K- pair. Differential and total cross sections are presented for the production of phi-mesons, decaying through phi -> K+K-, as well as for prompt K+K- production. The prompt production seems to follow phase space in both its differential distributions and in its energy dependence. The amplitude for the pd -> He-3 phi reaction varies little for excess energies below 22 MeV and the value is consistent with that obtained from a threshold measurement. The angular distribution of the K+K- decay pair shows that near threshold the phi-mesons are dominantly produced with polarization m=0 along the initial proton direction. No conclusive evidence for f(0)(980) production is found in the data.