Measurement of the reaction $γp \TO K^ + Λ(1520)$ at photon energies up to 2.65 GeV

Abstract

The reaction $γp \TO K^+Λ(1520)$ was measured in the energy range from threshold to 2.65 GeV with the SAPHIR detector at the electron stretcher facility ELSA in Bonn. The $\hat{I}›(1520)$ production cross section was analyzed in the decay modes $p{K}^{-}$, $n{\bar{K}}^0$, $\hat{I}{\pounds }^{\pm }\ddot{I}{€}^{\mp }$, and $\hat{I}›\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ as a function of the photon energy and the squared four-momentum transfer $t$. While the cross sections for the inclusive reactions rise steadily with energy, the cross section of the process $γp \TO K^+Λ(1520)$ peaks at a photon energy of about 2.0 GeV, falls off exponentially with $t$, and shows a slope flattening with increasing photon energy. The angular distributions in the $t$-channel helicity system indicate neither a $K$ nor a $K^{\star }$ exchange dominance. The interpretation of the $\hat{I}›(1520)$ as a $\hat{I}\pounds (1385)\ddot{I}€$ molecule is not supported.

11 pages, 16 figures, 4 tables