The reaction $pp \to p\Lambda K^+$ near threshold

N. Kaiser

doi:doi:10.1007/s100500050263

2022 Impact factor 2.7

Hadrons and Nuclei

Eur. Phys. J. A 5, 105-110

The reaction $pp \to p\Lambda K^+$ near threshold

N. Kaiser

Physik Department T39, Technische Universität München, D-85747 Garching, Germany

Received: 28 October 1998 / Revised version: 12 January 1999 Communicated by F. Lenz

Abstract
We analyze the recent total cross section data for $pp \to p\Lambda K^+$ near threshold measured at COSY. Using an effective range approximation for the on-shell $p\Lambda$ S-wave final state interaction we extract from these data the combination ${\cal K} = \sqrt{2\vert K_s\vert^2+\vert K_t\vert^2} = 0.38$ fm⁴ of the singlet (K_s) and triplet (K_t) threshold transition amplitudes. We present an exploratory calculation of various (tree-level) vector and pseudoscalar meson exchange diagrams. Pointlike $\omega$ -exchange alone and the combined ( $\rho^0,\omega,K^{*+}$ )-exchange can explain the experimental value of $\cal K$ . The pseudoscalar meson exchanges based on a SU(3) chiral Lagrangian turn out to be too large. However, when adding $\pi^0$ -exchange in combination with the resonant $\pi N \to S_{11}(1650)\to K \Lambda$ transition and introducing monopole form factors with a cut-off $\Lambda_c= 1.5$ GeV one is again able to reproduce the experimental value of $\cal K$ . More exclusive measurements are necessary to reveal the details of the $pp \to p\Lambda K^+$ production mechanism.