Measurement of $\Lambda$ baryon polarization in $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }$ at $\sqrt{s}=3.773$ GeV

Abstract

Using a data sample of $\psi (3770)$ events collected with the BESIII detector at BEPCII corresponding to an integrated luminosity of 2.9 fb${}^{-1}$, we report a measurement of $\Lambda$ spin polarization in $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }$ at $\sqrt{s}=3.773$ GeV. The significance of polarization is found to be 2$\sigma$ including the systematic uncertainty, which implies a zero phase between the transition amplitudes of the $\Lambda \bar{\Lambda }$ helicity states. This phase can be interpreted in terms of psionic form factors, and is determined to be $\Delta {\Phi }^{\Psi }$ = ${\Phi }_E^{\Psi }-{\Phi }_M^{\Psi }$ = $(71_{-46}^{+66}$ $\pm$ 5)${}^{\circ }$. Similarly, the ratio between the form factors is found to be $R^{\psi }$ = $|G_E^{\Psi }/G_M^{\Psi }|$ = $0.48_{-0.07}^{+0.12}$ $\pm$ 0.04. The first uncertainties are statistical and the second systematic.

8 pages, 9 figures, consistent with paper published in Phys. Rev. D (Letter) 105, L011101 (2022)

References in corpus (10)

• Nucleon Electromagnetic Form Factors
• Dispersion analysis of the nucleon form factors including meson continua
• ${\Sigma }^{+}$ and ${\bar{\Sigma }}^{-}$ polarization in the $J/\psi$ and $\psi (3686)$ decays
• Hyperon Form Factors & Diquark Correlations
• First Measurements of Timelike Form Factors of the Hyperons, Lambda0, Sigma0, Sigma+, Xi0, Xi-, and Omega-, and Evidence of Diquark Correlations
• Measurement of the cross section for $e^{+}{e}^{-}\to {\Xi }^{-}{\bar{\Xi }}^{+}$ and observation of an excited $\Xi$ baryon
• Measurement of cross section for $e^{+}{e}^{-}\to {\Xi }^0{\bar{\Xi }}^0$ near threshold
• Measurement of the cross section for $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }$ and evidence of the decay $\psi (3770)\to \Lambda \bar{\Lambda }$
• Measurements of Baryon Pair Decays of ${\chi }_{cJ}$ Mesons
• The Construction of the BESIII Experiment

Cited by in corpus (17)

• Measurement of the Energy-Dependent Electromagnetic Form Factors of a Charmed Baryon
• Observation of ${\Xi }^{-}$ Hyperon Transverse Polarization in $\psi (3686)\to {\Xi }^{-}{\bar{\Xi }}^{+}$
• First simultaneous measurement of ${\Xi }^0$ and ${\bar{\Xi }}^0$ asymmetry parameters in $\psi (3686)$ decay
• Study of $e^{+}{e}^{-}\to {\Omega }^{-}{\bar{\Omega }}^{+}$ at center-of-mass energies from 3.49 to 3.67 GeV
• Electromagnetic form factors of neutron and neutral stange hyperons in the oscillating view of point
• Predicted $\Lambda \bar{\Lambda }$ and ${\Xi }^{-}{\bar{\Xi }}^{+}$ decay modes of the charmoniumlike $Y(4230)$
• Measurement of the cross section of $e^{+}{e}^{-}\to {\Xi }^{-}{\bar{\Xi }}^{+}$ at center-of-mass energies between 3.510 and 4.843 GeV
• Production and decay of polarized hyperon-antihyperon pairs
• Production and decay of hyperons in a transversely polarized electron-positron collider
• $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross sections and the ${\Lambda }_c^{+}$ electromagnetic form factors within the extended vector meson dominance model
• Understanding oscillating features of the timelike nucleon electromagnetic form factors within the extending vector meson dominance model
• The cross section of the process $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }$ in the vicinity of charmonium $\psi (3770)$ including three-gluon and $D$-meson loop contributions
• The electromagnetic form factors and spin polarization of ${\Lambda }_c^{+}$ in the process $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$
• Measurement of Born cross section of $e^{+}{e}^{-}\to {\Sigma }^0{\bar{\Sigma }}^0$ at $\sqrt{s}=3.50-4.95$ GeV
• Observation of Transverse Polarization and Determination of Psionic Form Factors of the $\Lambda$ Hyperon at $\sqrt{s}=3.773$ GeV
• Observation of $\Xi (1530{)}^0$ Polarization and Determination of Its Electric and Magnetic Moments in $\psi (3686)\to \Xi (1530{)}^0\bar{\Xi }(1530{)}^0$
• Amplitude analysis and branching fraction measurement of $J/\psi \to \Lambda {\bar{\Sigma }}^0\eta +c.c$