${\mathrm{\ensuremath{\Sigma}}}^{+}$ and ${\overline{\mathrm{\ensuremath{\Sigma}}}}^{\ensuremath{-}}$ Polarization in the $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(3686)$ Decays

Open Access

${Σ しぐま}^{+}$ and ${\bar{Σ しぐま}}^{-}$ Polarization in the $J / ψ ぷさい$ and $ψ ぷさい (3686)$ Decays

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. Lett. 125, 052004 – Published 31 July 2020

Abstract

From $1310.6 \times 10^{6} J / ψ ぷさい$ and $448.1 \times 10^{6} ψ ぷさい (3686)$ events collected with the BESIII experiment, we report the first observation of ${Σ しぐま}^{+}$ and ${\bar{Σ しぐま}}^{-}$ spin polarization in $e^{+} e^{-} \to J / ψ ぷさい [ψ ぷさい (3686)] \to {Σ しぐま}^{+} {\bar{Σ しぐま}}^{-}$ decays. The relative phases of the form factors $Δ でるた Φ ふぁい$ have been measured to be $(- 15.5 \pm 0.7 \pm 0.5) °$ and $(21.7 \pm 4.0 \pm 0.8) °$ with $J / ψ ぷさい$ and $ψ ぷさい (3686)$ data, respectively. The nonzero value of $Δ でるた Φ ふぁい$ allows for a direct and simultaneous measurement of the decay asymmetry parameters of ${Σ しぐま}^{+} \to p {π ぱい}^{0} ({α あるふぁ}_{0} = - 0.998 \pm 0.037 \pm 0.009)$ and ${\bar{Σ しぐま}}^{-} \to \bar{p} {π ぱい}^{0} ({\bar{α あるふぁ}}_{0} = 0.990 \pm 0.037 \pm 0.011)$ , the latter value being determined for the first time. The average decay asymmetry, $({α あるふぁ}_{0} - {\bar{α あるふぁ}}_{0}) / 2$ , is calculated to be $- 0.994 \pm 0.004 \pm 0.002$ . The $C P$ asymmetry $A_{C P, Σ しぐま} = ({α あるふぁ}_{0} + {\bar{α あるふぁ}}_{0}) / ({α あるふぁ}_{0} - {\bar{α あるふぁ}}_{0}) = - 0.004 \pm 0.037 \pm 0.010$ is extracted for the first time, and is found to be consistent with $C P$ conservation.

Received 17 April 2020
Accepted 18 June 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.052004

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Published by the American Physical Society