Polarization observables in the $e^{+}e^{-} \rightarrow \bar{\Lambda}\Lambda$ reaction

Abstract.

Cross-section, vector-polarization, and tensor-polarization distributions are calculated for the reactions $e^{+}e^{-}\rightarrow\bar{p}p$ and $e^{+}e^{-}\rightarrow \bar{\Lambda}\Lambda$. Each reaction requires six characteristic functions that are bilinear in the, possibly complex, electromagnetic form factors, denoted $G_{E}(P^{2})$ and $G_{M}(P^{2})$, of p and $\Lambda$. For the hyperon reaction also the joint-decay distributions of $\Lambda$ and $\bar{\Lambda}$ are calculated. Their knowledge allows a complete determination of the hyperon electromagnetic form factors, without measuring hyperon spins. We explain how this is done in practice. For some tensor-polarization components our results are in conflict with previously repeatedly published distributions.