Observation of Transverse $\Lambda /\overline{\Lambda }$ Hyperon Polarization in ${e}^{+}{e}^{-}$ Annihilation at Belle

29 January 2019

Abstract: We report the first observation of the spontaneous polarization of $\Lambda$ and $\overline{\Lambda }$ hyperons transverse to the production plane in ${e}^{+}{e}^{-}$ annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive $\Lambda /\overline{\Lambda }$ production, we also report results with subtracted feed-down contributions from ${\Sigma }^{0}$ and charm. This measurement uses a dataset of $800.4\text{}\text{}{\mathrm{fb}}^{-1}$ 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 $\Lambda /\overline{\Lambda }$ hyperon.

Published in: Physical Review Letters 122 (2019)