String model description of polarisation and angular distributions in pbar p -> Lambdabar Lambda at low energies

Abstract

The observed polarisation of Lambda hyperons from the inclusive pA -> Lambda X reaction at high energies has previously been well described within the Lund string model through polarised ss quark pair production in the string breaking hadronisation process. This model is here applied to the exclusive pbar p -> Lambdabar Lambda reaction at low energies and compared to available data sets down to an incident beam momentum of 1.835 GeV/c. This required an extension of the diquark scattering model to involve three components: an isotropic part relevant close to threshold, a spectator part and a forward scattering part as in pA -> Lambda X at high energies. The observed angular distributions are then reproduced and, for momentum transfers above |t'| = 0.2 GeV^2, agreement with the measured polarisation is also obtained.