Speaker
Description
In present work we study the production of ground and excited charmonium states in $e^- e^+ \rightarrow \gamma+ \eta_c(nS)/\chi_{cJ}(nP)(J=0,1)$ [1] through leading order (LO) (tree-level) diagrams, which proceed through exchange of a virtual photon that couples to $\gamma$ and $\eta_c/\chi_{cJ}$ through the triangular quark loop diagram, in the framework of $4\times 4$ Bethe-Salpeter equation (BSE), at center of mass energy, $\sqrt{s}=10.6 GeV.$ With use of Covariant Instantaneous Ansatz, we have been able to express the "3D form" of the amplitude, $M_{fi}$ as a linear superposition of terms involving combinations of $++$, and $--$ components of Salpeter wave functions of final hadron, whose general form is relativistically covariant, and is expressible in terms of the form factors [1]. This work is an extension of previous applications of this method to calculate decay widths of E1 and M1 radiative transitions[2] involving various quarkonia. In the present work, the cross sections for these processes with leading order (tree) level diagrams alone at $\sqrt{s}=10.6 GeV.$ provide a sizable contribution, which might be mainly due to the BSE being a fully relativistic approach that incorporates the relativistic effect of quark spins and can also describe internal motion of constituent quarks within the hadron in a relativistically covariant manner. Our results are compared with the recent data of Belle collaboration[3], and other models,
References:
[1] S.Bhatnagar, V.Guleria, arxiv:2206.02229[hep-ph]v2 (to be submitted soon).
[2] V.Guleria,E.Gebrehana, S.Bhatnagar,Phys. Rev. D104, 094045(2021).
[3] S.Jia et al.,(Belle Collaboration), Phys. Rev. D 98, 092015 (2018).
| speaker affiliation | Department of Physics, Chandigarh University |
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