Radiative decays of the predicted P-wave $D\bar{D}^*$ molecular state: the $0^{-+}$ case

Abstract: In the present work, we study the radiative decays of the P-wave $D\bar{D}<sup>*$ molecular state $G_0$ with $I<sup>G(J<sup>{PC})=0<sup>+(0<sup>{-+})$ using a phenomenological Lagrangian approach. The molecular coupling is fixed by the compositeness condition with a Gaussian form factor. The partial widths for $G_0\to γγ$, $γJ/ψ$, $γψ(2S)$, $γh_c$, $γρ$, and $γω$ are evaluated. Our results show that the two-photon and $γh_c$ channels are highly suppressed, while $γJ/ψ$, $γψ(2S)$, and $γρ$ are of the order of a few keV, and $γω$ reaches several tens of keV, making it the dominant radiative mode. The ratios $Γ(G_0 \to γψ(2S))/Γ(G_0 \to γJ/ψ)$ and $Γ(G_0 \to γω)/Γ(G_0 \to γρ)$ are predicted to be 1-2.6 and 3.4-5.4, respectively, with mild parameter dependence. We also compare with hadronic decays and find that the total radiative decay width is lower than the hadronic decay widths by about one order of magnitude. We propose searching for $G_0$ in the sequential decay $Y(4230)\to γG_0 \to γωJ/ψ$, which is accessible to further experimental measurements by the BESIII, Belle II and LHCb Collaborations.