The electromagnetic form factors of $$\Lambda _c$$ hyperon in the vector meson dominance model

Abstract

We apply a modified vector meson dominance (VMD) model to analyze the electromagnetic form factors of the c hyperon in the time-like reaction e + e − → + c ¯ − c . In the model, we include the contributions from the vector charmed mesons and their excitations ψ(1S), ψ(2S), ψ(3770), ψ(4040), ψ(4160) and ψ(4415). We perform a combined fit to the available data on the Born cross section in reaction e + e − → + c ¯ − c and the ratio of the electromagnetic form factors |G E /G M | to obtain the values of the model parameters. Our results show that the VMD model can simultaneously describe the data of electromagnetic form factors from the Belle and BESIII Collaborations, and the behavior of |G E /G M | for the BESIII data can be qualitatively reproduced by the VMD model prediction at the threshold region. Moreover, we predict the single and double polarization observables in e + e − → + c ¯ − c reactions, which are experimentally accessible in the polarized process. We also obtain the form factors of the c hyperon in the space-like region via analytic continuing the time-like

Electromagnetic Form Factors of Λ Hyperon in the Vector Meson Dominance Model and a Possible Explanation of the Near-Threshold Enhancement of the e+e−→ΛΛ¯ Reaction

“…The EMFFs of baryons have been studied with the VMD model for the proton, [21−24] 𝛬 hyperon, [16] 𝛴 hyperon, [25] and charmed 𝛬 + 𝑐 baryon. [26] Following Ref. [16], we revisit the EMFFs of 𝛬 hyperon and the 𝑒 + 𝑒 − → 𝛬 Λ reaction near threshold by employing the modified VMD model.…”

e+e−→Λc+Λ¯c− Cross Sections and the Λc+ Electromagnetic Form Factors within the Extended Vector Meson Dominance Model

“…Note that all the above-mentioned charmonium states considered in Ref. [19] are below the mass threshold of 𝛬 +…”

“…[18] Moreover, the EMFFs of 𝛬 + 𝑐 were investigated by virtue of the VMD model in Ref. [19], where these charmonium states 𝐽/𝜓(1𝑆), 𝜓(2𝑆), 𝜓(3770), 𝜓(4040), 𝜓(4160), and 𝜓(4415) were included in the model. Note that all the above-mentioned charmonium states considered in Ref.…”

“…[20] Hence, these nonmonotonic structures above the 𝛬 + 𝑐 Λ− 𝑐 threshold cannot be described by the model. [19] Very recently, the BESIII Collaboration published the new measurements of the 𝑒 + 𝑒 − → 𝛬 + 𝑐 Λ− 𝑐 reaction. [21] It is found that there is no peak around the energy of 𝑌 (4630), but, a long platform behavior from the reaction threshold to 4.66 GeV was observed, diverging from the Belle measurements around that energy region.…”