Observation of Transverse Λ / Λ Hyperon Polarization in e+e- Annihilation at Belle

Abstract

We report the first observation of the spontaneous polarization of Λ and Λ hyperons transverse to the production plane in e+e- annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive Λ/Λ production, we also report results with subtracted feed-down contributions from Σ0 and charm. This measurement uses a dataset of 800.4 fb-1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the Λ/Λ hyperon.