Is the existence of a J/ψJ/ψ bound state plausible?

In a recent measurement LHCb reported pronounced structures in the J/psi J/psi spectrum. One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia. It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons, which hadronise into two pions at the longest distance. In this paper, we demonstrate that, given our current understanding of hadron-hadron interactions, the exchange of correlated light mesons (pions and kaons) is able to provide sizeable attraction to the di-J/psi system, and it is possible for two J/psi mesons to form a bound state. As a side result we find from an analysis of the data for the psi(2S) -> J/psi pi pi transition including both pi pi and K (K) over bar final state interactions an improved value for the psi(2S) -> J/psi transition chromo-electric polarisability: vertical bar alpha psi(2S)J/psi vertical bar = (1.8 +/- 0.1) GeV-3, where the uncertainty also includes the one induced by the final state interaction. (C) 2021 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Automated summary

By analyzing the data, an improved value for the psi(2S) -> J/psi transition chromo-electric polarisability was found, which includes both pi pi and K (K) over bar final state interactions.