Polarization observables in $e^{+}{e}^{-}$ annihilation to a baryon-antibaryon pair

Abstract

Using the helicity formalism of Jacob and Wick we derive spin density matrices of baryon antibaryon pairs produced in $e^{+}{e}^{-}$ annihilation. We consider the production of pairs with spins $1/2+\overline{1/2}$, $1/2+\overline{3/2}$ (+c.c.) and $3/2+\overline{3/2}$. We provide modular expressions to include chains of weak hadronic two-body decays of the produced hyperons. The expressions are suitable for the analysis of high statistics data from $J/\psi$ and $\psi (2S)$ decays at $e^{+}{e}^{-}$ colliders, by fits to the fully differential angular distributions of the measured particles. We illustrate the method by examples, such as the inclusive measurement of the $e^{+}{e}^{-}\to \psi (2S)\to {\Omega }^{-}{\bar{\Omega }}^{+}$ process where one decay chain ${\Omega }^{-}\to \Lambda K^{-}$ followed by $\Lambda \to p{\pi }^{-}$ is considered. Finally we show that the inclusive angular distributions can be used to test spin assignment of the produced baryons.

arXiv comment16 pages;update: 1 figure, extended introduction and examples, results not changed

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• Determination of the ${\Lambda }_c^{+}$ spin via the reaction $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$
• Prospects to study hyperon-nucleon interactions at BESIII
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• Precise Measurement of Matter-Antimatter Asymmetry with Entangled Hyperon Antihyperon Pairs
• Parametrizations of the Spin Density Matrix
• Observation of Transverse Polarization and Determination of Psionic Form Factors of the $\Lambda$ Hyperon at $\sqrt{s}=3.773$ GeV
• Sequential decays of the triple strange process $\bar{p}p\to {\bar{\Omega }}^{+}{\Omega }^{-}\to K^{+}\bar{\Lambda }{K}^{-}\Lambda \to K^{+}\bar{p}{\pi }^{+}{K}^{-}p{\pi }^{-}$: a model-independent approach
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