Speaker
Description
We investigate strong and radiative decays of low-lying conventional charmonium and exotic charmonium-like states, recently reported by the Belle-II and BES-III Collaborations, within the covariant confined quark model.
A unified description of $S$- and $P$-wave radiative transitions of six charmonium states ($\eta_c$, $J/\psi$, $\chi_{cJ}$, $h_c$) is given with a single parameter $\varrho$. The value of $\Gamma(J/\psi\to\gamma\eta_c)$ is predicted, and the transition $h_c\to\gamma\eta_c$ is calculated for the first time, yielding an indirect estimate of $\Gamma_{\text{tot}}(h_c)$. The deconfinement limit $\lambda\to0$ confirms the stability and internal consistency of the approach.
Three-particle strong decays of exotic states are described through intermediate scalar resonances for the first time, with the broad $f_0(500)\to\pi^+\pi^-$ dominating over the narrow $f_0(980)$; a modified Breit-Wigner function significantly reduces $\Gamma(Y\to K^+K^-J/\psi)$, and for $Y(4230)$ the theoretical ratio of $K^+K^-J/\psi$ to $\pi^+\pi^-J/\psi$ agrees with BESIII data.
Isospin violation in hidden-charm strong decays of $X_2(4014)$ is studied, treating it as a molecular four-quark state. The calculated partial widths for $\omega J/\psi$ and $\rho^0 J/\psi$ agree with recent data. The predicted ratio $\mathrm{BR}_{X_2}\approx1.14$ is insensitive to mass deviations and free of threshold singularities, providing an experimentally testable criterion for a molecular (tetraquark) interpretation.
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Refs:
Gurjav Ganbold \textit{et al.}, Phys. Rev. D \textbf{104}, 094048 (2021).
Gurjav Ganbold and M. A. Ivanov, Eur. Phys. J. A 60, 13 (2024).
Gurjav Ganbold and M. A. Ivanov, Phys. Rev. D \textbf{111}, 014007 (2025). \
