Protoninduced Pion-, Eta- and Kaon-Production at Threshold

Abstract

We present some details of our recent theoretical investigations on the total cross section of the reactions $pp\to pp{\pi }^0$, $pp\to pp\eta$ and $pp\to p\Lambda K^{+}$ at threshold. Applying standard nonrelativistic perturbation theory within the framework of meson exchange models (MEC) to all of the investigated processes we observe that theory is still far--off from a quantitative understanding of the existing data, although the qualitative behaviour of the threshold cross sections can be reproduced. The often quoted ${\eta }^2$--dependence of the $pp\to pp{\pi }^0$ cross section at threshold is due to a calculational mistake of Koltun and Reitan (1966) and not based on theoretical grounds, where threebody phasespace behaviour would yield ${\eta }^4$, which can be affected by final state and short range effects. To respect the high momentum transfers for $pp\to pp\eta$ and $pp\to p\Lambda K^{+}$ relativistic models were developed. Hereby the $\eta$--production still is based on MEC, while the $K^{+}$ production was investigated in the quark-gluon-picture based on the Bethe--Salpeter formalism.

Comments: 4 pages; contribution to BARYONS98, Bonn, Germany, September 1998