Producing fully-charm structures in the $J/\psi$-pair invariant mass spectrum

TL;DR

This paper proposes a dynamical mechanism to explain the enhancements observed in the $J/$-pair invariant mass spectrum by LHCb, and predicts similar structures in the $mbda(1S)$-pair spectrum in the $bar{b}$ system.

Contribution

The work introduces a novel dynamical model that reproduces LHCb's di-$J/$ data and predicts potential enhancements in di-$mbda(1S)$ spectra for future experimental verification.

Findings

Successfully reproduces LHCb di-$J/$ mass spectrum data.

Predicts possible enhancements near 19.0, 19.3, 19.7 GeV in $mbda(1S)$-pair spectrum.

Provides a framework for understanding fully-charm and fully-bottom tetraquark structures.

Abstract

Very recently, the LHCb Collaboration reported the observation of several enhancements in the invariant mass spectrum of a $J/\psi$ pair between 6.2 and 7.4 GeV. In this work, we propose the dynamical mechanism to mimic the experimental data of a di-$J/\psi$ mass spectrum given by LHCb, which is based on the reactions, where all the possible combinations of a double charmonium directly produced by a proton-proton collision are transferred into a final state $J/\psi J/\psi$. We find that the LHCb experimental data can be well reproduced. We further extend our framework to study a di-$\Upsilon(1S)$ system, and give the line shape of a differential cross section of a partner process in a $b\bar{b}$ system on the invariant mass of $\Upsilon(1S)\Upsilon(1S)$, which shows that there should exist possible enhancements near $m_{\Upsilon(1S)\Upsilon(1S)}=$19.0, 19.3, 19.7 GeV in the $\Upsilon(1S)$-pair invariant mass spectrum. These predictions can be tested in LHCb and CMS, which can be as a potential research issue in near future.