A Fit to the Available e+e− → Λc+Λ¯c− Cross Section Data Nearby Production Threshold by Means of a Strong Correction to the Coulomb Enhancement Factor

Abstract

There are two available sets of data on the e+e−→Λc+Λ¯c− cross section at energies close to the production threshold, collected by the Belle and by the BESIII Collaborations. The measurement of the former, performed by means of the initial state radiation technique, is compatible with the presence of a resonance, called ψ(4660), observed also in other final states. On the contrary, the latter is measured an almost flat and hence non-resonant cross section in the energy region just above the production threshold, but the data stop before the possible rise in the cross section for the resonant production. We propose an effective model to describe the behavior of the data near this threshold, which is based on a Coulomb-like enhancement factor due to the strong interaction among the final state particles. In the framework of this model, it is possible to describe both datasets.

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

“…This new experimental result stimulates further research on the EMFFs of 𝛬 + 𝑐 and the 𝑒 + 𝑒 − → 𝛬 + 𝑐 Λ− 𝑐 reaction near threshold. [22,23] In the present work, based on the new measurements by the BESIII Collaboration on the 𝑒 + 𝑒 − → 𝛬 + 𝑐 Λ− 𝑐 reaction, [21] we devoted to studying the EMFFs in the time-like region of 𝛬 + 𝑐 within an extended vector meson dominance model. In the VMD model, the electromagnetic form factors of the baryons are attributed to both the couplings of the virtual photon to the vector mesons and the vector mesons to the baryons.…”