### Note on rare -boson Decays to Double Heavy Quarkonia

Dao-Neng Gao (, Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, , Hefei 230026, , China,) ; Xi Gong (, Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, , Hefei 230026, , China,)

Within the standard model, we have investigated rare Z-boson decays into double heavy quarkonia, $Z\to VV$ and $Z\to VV$ , with V and P denoting vector and pseudoscalar quarkonia, respectively. It is assumed that the leading-order QCD diagrams would give the dominant contributions to these processes, and the corresponding branching fractions, for instance, $Z\to VV$ , have been estimated to be approximately $Z\to VV$ in literature. However, these decays could also happen through electromagnetic transitions $Z\to VV$ and $Z\to VV$ , with the virtual photon transforming into V. Interestingly, the smallness of the vector quarkonium mass can give rise to a large factor $Z\to VV$ relative to the QCD contributions, which thus counteracts the suppression from the electromagnetic coupling. We systematically include these two types of contributions in our calculation to predict branching fractions for these decays. Particularly, owing to the virtual photon effects, it is found that $Z\to VV$ will be significantly enhanced, up to $Z\to VV$ .

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"title": "Note on rare -boson Decays to Double Heavy Quarkonia  "
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Published on:
01 April 2023
Publisher:
IOP
Published in:
Chinese Physics C , Volume 47 (2023)
Issue 4
Article ID: 043106
DOI:
https://doi.org/10.1088/1674-1137/acb7d1
arXiv:
2208.12652