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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• Design and Construction of the BESIII Detector
• Diquarks and Exotic Spectroscopy
• Exotica
• Baryons as relativistic three-quark bound states
• High-precision determination of the electric and magnetic form factors of the proton
• Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data
• Precision Rosenbluth measurement of the proton elastic form factors
• Matching perturbative and Parton Shower corrections to Bhabha process at flavour factories
• Final Analysis of Proton Form Factor Ratio Data at ${\mathbf{Q}}^2=4.0$, 4.8 and 5.6 GeV${}^2$
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• Precision Measurements of the Timelike Electromagnetic Form Factors of Pion, Kaon, and Proton
• Leading SU(3)-breaking corrections to the baryon magnetic moments in Chiral Perturbation Theory
• Exclusive event generator for $e^{+}{e}^{-}$ scan experiments
• Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass
• Measurement of proton electromagnetic form factors in $e^{+}{e}^{-}\to p\bar{p}$ in the energy region 2.00-3.08 GeV
• Precision measurement of the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross section near threshold
• Photon pair production at flavour factories with per mille accuracy
• Dispersion-theoretical analysis of the nucleon electromagnetic form factors: Inclusion of time-like data
• Observation of a cross-section enhancement near mass threshold in $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }$
• Measurement of the proton form factor by studying $e^{+}{e}^{-}\to p\bar{p}$
• Unexpected features of e+e-->ppbar and e+e-->lambda-lambdabar cross sections near threshold
• Study of the process $e^{+}{e}^{-}\to p\bar{p}$ in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector
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• Hyperon Form Factors & Diquark Correlations
• Complete measurement of $\Lambda$ electromagnetic form factors
• Octet baryon electromagnetic form factors in nuclear medium
• Luminosity measurements for the R scan experiment at BESIII
• Polarization observables in the $e^{+}{e}^{-}\to \bar{\Lambda }\Lambda$ reaction
• Hyperon electromagnetic timelike elastic form factors at large $q^2$
• Using baryon octet magnetic moments and masses to fix the pion cloud contribution
• Re-examining the $X(4630)$ resonance in the reaction $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$
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• Strong and electromagnetic amplitudes of the $J/\psi$ decays into baryons and their relative phase
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• First Measurements of ${\chi }_{cJ}\to {\Sigma }^{-}{\bar{\Sigma }}^{+}(J=0,1,2)$ Decays

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• Probing the internal structure of baryons
• Timelike nucleon electromagnetic form factors: All about interference of isospin amplitudes
• Study of $e^{+}{e}^{-}\to {\Omega }^{-}{\bar{\Omega }}^{+}$ at center-of-mass energies from 3.49 to 3.67 GeV
• Electromagnetic form factors of the ${\Omega }^{-}$ baryon in the spacelike and timelike regions
• Toy model to understand oscillatory behavior in timelike nucleon form factors
• The $\Sigma$ and $\Xi$ electromagnetic form factors in the extended vector meson dominance model
• Determination of the ${\Sigma }^{+}$ Timelike Electromagnetic Form Factors
• Electromagnetic form factors of neutron and neutral stange hyperons in the oscillating view of point
• Production and decay of polarized hyperon-antihyperon pairs
• Study of $e^{+}{e}^{-}\to {\Sigma }^0\overline{\Sigma }{}^0$ and ${\Sigma }^{+}\overline{\Sigma }{}^{-}$ by Initial State Radiation Method at Belle
• Electromagnetic $|G_E/G_M|$ ratios of hyperons at large timelike $q^2$
• $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross sections and the ${\Lambda }_c^{+}$ electromagnetic form factors within the extended vector meson dominance model
• Electromagnetic form factors of ${\Sigma }^{+}$ and ${\Sigma }^{-}$ in the vector meson dominance model
• Development of a Data-Driven Method to Simulate the Detector Response of Anti-neutron at BESIII
• Higher strangeonium decays into light flavor baryon pairs like $\Lambda \bar{\Lambda }$, $\Sigma \bar{\Sigma }$, and $\Xi \bar{\Xi }$
• 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
• Compared analysis of time-like hyperon form factors
• The electromagnetic form factors of ${\Lambda }_c$ hyperon in the vector meson dominance model
• Precise measurement of the branching fractions of $J/\psi \to \bar{\Lambda }{\pi }^{+}{\Sigma }^{-}+c.c.$ and $J/\psi \to \bar{\Lambda }{\pi }^{-}{\Sigma }^{+}+c.c.$
• The electromagnetic form factors and spin polarization of ${\Lambda }_c^{+}$ in the process $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$
• Measurements of Born Cross Sections for $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c(2595{)}^{-}+c.c.$ and $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c(2625{)}^{-}+c.c.$ at $\sqrt{s}=$4918.0 and 4950.9 MeV
• Unraveling the structure of $\Lambda$ hyperons with polarized $\Lambda \bar{\Lambda }$ pairs
• Observation of Transverse Polarization and Determination of Psionic Form Factors of the $\Lambda$ Hyperon at $\sqrt{s}=3.773$ GeV
• Accessing baryon-antibaryon generalized distribution amplitudes in $e^{\pm }\gamma \to e^{\pm }B\bar{B}$
• A description of charmonia decays $J/\psi \to B\bar{B}$ within the QCD factorisation framework