A Quark Model of Lambdabar-Lambda Production of Pbar-P Interactions

A quark model which includes both scalar and vector contributions to the reaction mechanism (SV quark model) is used in a DWBA calculation of $\bar \Lambda \Lambda$ production in $\bar p p$ interractions. Total and differential cross-sections, polarizations, depolarizations, and spin-correlattion coefficients are computed for laboratory momenta from threshold to 1695 MeV/c. The free parameters of the calculation are the scalar and vector strengths, a quark cluster size parameter,and the parameters of the unknown $\bar \Lambda \Lambda$ potentials. Good agreement with experiment is found for constructive interference of the scalar and vector terms, and for $\bar \Lambda \Lambda$ potentials which differ from those suggested by several authors on the basis of SU(3) arguments. The fit to the data is better than that obtained by other quark models, which use only scalar $or$ vector annihilation terms. The agreement with experiment is also better than that found in meson-exchange models. The recent suggestion[1] that measurement of the depolarization parameter $D_{nn}$ can be used to discriminatebetween meson-exchange and quark models is examined in detail. We conclude that a measurement of $D_{nn}$ will provide a test of which of these models, as presently constructed,is the more appropriate description of strangeness production in the $\bar p p \ rightarrow \bar \Lambda \Lambda$ reaction.