Polarization observables in the reaction

Göran Fäldt

doi:10.1140/epja/i2016-16141-y

EPJ

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2023 Impact factor 2.6

Hadrons and Nuclei

Eur. Phys. J. A (2016) 52: 141
https://doi.org/10.1140/epja/i2016-16141-y

Regular Article - Theoretical Physics

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

Göran Fäldt^*

Department of physics and astronomy, Uppsala University, Box 516, S-751 20, Uppsala, Sweden

^* e-mail: goran.faldt@physics.uu.se

Received: 5 February 2016
Revised: 15 April 2016
Accepted: 17 April 2016
Published online: 25 May 2016

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.