Study of the $pd{\to }^3\text{He}{K}^{+}{K}^{-}$ and $pd{\to }^3\text{He}\varphi$ reactions close to threshold

Abstract

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 ${}^3$He and a vertex detector to measure the $K^{+}{K}^{-}$ pair. Differential and total cross sections are presented for the production of $\varphi$--mesons, decaying through $\varphi \to K^{+}{K}^{-}$, 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 $pd{\to }^3${He}$\varphi$ 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 $\varphi$--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.

Comments: 13 figures