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.
Highlights
The measurement of the baryon-anti-baryon cross section from electron-positron annihilation has attracted great interest in recent years, especially in the region near to the production threshold, partially owing to the efforts of the BESIII Collaboration
The fit quality is reasonable, since the reduced χ2 = 2. This is mainly due to the large error bars of the Belle data
The red dots with error bars are the BESIII experimental data [11], the blue squares are the BELLE data [6], and the red line is the fit result with the formula on Equation (6) modified as described in the text
Summary
The measurement of the baryon-anti-baryon cross section from electron-positron annihilation has attracted great interest in recent years, especially in the region near to the production threshold, partially owing to the efforts of the BESIII Collaboration. We propose a model to explain the phenomenon of the steep rise in the cross section at the threshold, which is described in terms of a Coulomb-like enhancement effect [15], due to the strong interaction of the final baryons. By considering this effect, we parametrize the lineshape of the cross section in the case of resonant behavior around the ψ(4660) resonance, to show that it is possible to reconcile simultaneously both the available BESIII [11] and Belle [6] datasets. Since the threshold behavior is our focus, we decided to consider only those data that are definitely above it, instead of correcting for the aforementioned effect
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