Measurement of Spin Transfer Observables in Antiproton-Proton -> Antilambda-Lambda at 1.637 GeV/c

摘要

Spin transfer observables for the strangeness-production reactionAntiproton-Proton -> Antilambda-Lambda have been measured by the PS185collaboration using a transversely-polarized frozen-spin target with anantiproton beam momentum of 1.637 GeV/c at the Low Energy Antiproton Ring atCERN. This measurement investigates observables for which current models of thereaction near threshold make significantly differing predictions. Those modelsare in good agreement with existing measurements performed with unpolarizedparticles in the initial state. Theoretical attention has focused on the factthat these models produce conflicting predictions for the spin-transferobservables D_{nn} and K_{nn}, which are measurable only with polarized targetor beam. Results presented here for D_{nn} and K_{nn} are found to be indisagreement with predictions from existing models. These results alsounderscore the importance of singlet-state production at backward angles, whilecurrent models predict complete or near-complete triplet-state dominance.