Measurements of Sigma+ and Sigma- Time-like Electromagnetic Form Factors for center-of-mass energies from 2.3864 to 3.0200 GeV

Abstract

The Born cross sections of the $e^{+}{e}^{-}\to {\Sigma }^{+}{\bar{\Sigma }}^{-}$ and $e^{+}{e}^{-}\to {\Sigma }^{-}{\bar{\Sigma }}^{+}$ processes are determined with high precision for center-of-mass energy from 2.3864 to 3.0200 GeV with the BESIII detector. Nonzero cross sections near threshold are observed. The resulting ratio of effective form factors for the ${\Sigma }^{+}$ and ${\Sigma }^{-}$ is consistent with 3, agreeing with the ratio of the incoherent sum of the squared charges of the ${\Sigma }^{+}$ and ${\Sigma }^{-}$ valence quarks, but disagreeing with various theoretical predictions. In addition, ratios of the ${\Sigma }^{+}$ electric and magnetic form factors, $|G_E/G_M|$, are obtained at three center-of-mass energies through an analysis of the angular distributions. These measurements, which are studied for the first time in the off-resonance region, provide precision experimental input for understanding baryonic structure. The observed novel features of the ${\Sigma }^{\pm }$ form factors require a new theoretical description for the hyperons.

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Cited by in corpus (27)

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• Precise measurement of the branching fractions of $J/\psi \to \bar{\Lambda }{\pi }^{+}{\Sigma }^{-}+c.c.$ and $J/\psi \to \bar{\Lambda }{\pi }^{-}{\Sigma }^{+}+c.c.$
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• Accessing baryon-antibaryon generalized distribution amplitudes in $e^{\pm }\gamma \to e^{\pm }B\bar{B}$
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