arXiv:2606.24189·v1·High Energy Physics — Phenomenology

Rare Radiative Decays of Z boson into S- and P-wave Charmonium within the Bethe-Salpeter Model

Asif Ali🇨🇳 · Yi-Jie Li🇨🇳 · Guang-Zhi Xu🇨🇳 · Kui-Yong Liu🇨🇳

Abstract

We employ the Bethe-Salpeter (BS) model to investigate radiative decays of the Z boson into charmonium. Within the instantaneous approximation of the BS equation, we analyze the relevant decay channels for S-wave charmonium states ( $ψ (n S)$ , $η_{c} (n S)$ , $n = 1, 2, 3$ ) and P-wave charmonium states ( $χ_{c 0} (m P)$ , $χ_{c 1} (m P)$ , $h_{c} (m P)$ , $m = 1, 2$ ). We compute all branching fractions using leading-order Feynman diagrams. For the $J / ψ$ channel, our BS calculations suggest that prior theoretical results were likely underestimated, making our prediction more promising for future experimental measurements.

Comments: 29 pages, 6 figures, 3 tables