Search

Last year, the $\Xi(1620)$ state that is cataloged in the Particle Data Group (PDG) with only one star is reported again in the $\Xi^{-}\pi^{+}$ final state by the Belle Collaboration. Its properties not only the spectroscopy but also the decay width cannot be simply explained in the context of conventional constituent quark models. This intrigues an active discussion on the structure of this resonance. In this work, we study the radiative decays of the newly observed $\Xi(1620)$ assuming that it is a meson-baryon molecular state of $\Lambda\bar{K}$ and $\Sigma\bar{K}$ with spin-parity $J^P=1/2^{-}$ in our previous work. The partial decay widths of the $\Lambda\bar{K}-\Sigma\bar{K}$ molecular state into $\Xi\gamma$ and $\Xi\pi\gamma$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $\Xi(1620)^0\to\gamma\Xi$ and $\Xi(1620)^0\to\gamma\Xi\pi$ are evaluated to be about $118.76-174.21$ KeV and $58.19-68.75$ eV, respectively, which may be accessible for the LHCb. If the $\Xi(1620)$ is $\Lambda\bar{K}-\Sigma\bar{K}$ molecule, the radiative transition strength $\Xi(1620)^0\to\gamma\bar{K}\Lambda$ is quite small and the decay width is of the order of 0.01 eV. Future experimental measurements of these processes can be useful to test the molecule interpretations of the $\Xi(1620)$.

Last year, the $��(1620)$ state that is cataloged in the Particle Data Group (PDG) with only one star is reported again in the $��^{-}��^{+}$ final state by the Belle Collaboration. Its properties not only the spectroscopy but also the decay width cannot be simply explained in the context of conventional constituent quark models. This intrigues an active discussion on the structure of this resonance. In this work, we study the radiative decays of the newly observed $��(1620)$ assuming that it is a meson-baryon molecular state of $��\bar{K}$ and $��\bar{K}$ with spin-parity $J^P=1/2^{-}$ in our previous work. The partial decay widths of the $��\bar{K}-��\bar{K}$ molecular state into $����$ and $������$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $��(1620)^0\to����$ and $��(1620)^0\to������$ are evaluated to be about $118.76-174.21$ KeV and $58.19-68.75$ eV, respectively, which may be accessible for the LHCb. If the $��(1620)$ is $��\bar{K}-��\bar{K}$ molecule, the radiative transition strength $��(1620)^0\to��\bar{K}��$ is quite small and the decay width is of the order of 0.01 eV. Future experimental measurements of these processes can be useful to test the molecule interpretations of the $��(1620)$.

The $\Xi_b(6227)$ baryon with the quantum number $J^P=1/2^{-}$ is considered as a molecular state composed of a $\Sigma_b$ baryon and $\bar{K}$ meson. The partial decay widths of the $\Sigma_b\bar{K}$ molecular state into $\Xi_b\gamma$ and $\Xi_b^{'}\gamma$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $\Xi_b(6227)\to\gamma\Xi_b$ and $\Xi_b(6227)\to\gamma\Xi^{'}_b$ are evaluated to be about 1.50-1.02 KeV and 17.56-24.91 KeV, respectively, which may be accessible for the LHCb. Based on our results we argue that an experimental determination of the radiative decay width of $\Xi_b(6227)$ is important for the understanding of its intrinsic properties.

The $��_b(6227)$ baryon with the quantum number $J^P=1/2^{-}$ is considered as a molecular state composed of a $��_b$ baryon and $\bar{K}$ meson. The partial decay widths of the $��_b\bar{K}$ molecular state into $��_b��$ and $��_b^{'}��$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. The partial widths for the $��_b(6227)\to����_b$ and $��_b(6227)\to����^{'}_b$ are evaluated to be about 1.50-1.02 KeV and 17.56-24.91 KeV, respectively, which may be accessible for the LHCb. Based on our results we argue that an experimental determination of the radiative decay width of $��_b(6227)$ is important for the understanding of its intrinsic properties.

Very recently, three new structures $��_c(2923)^0$, $��(2938)^0$, and $��(2964)^0$ at the invariant mass spectrum of $��_c^{+}K^{-}$ observed by the LHCb Collaboration triggers a hot discussion about their inner structure. In this work, we study the strong decay mode of the newly observed $��_c$ assuming that the $��_c$ is a $\bar{D}��-\bar{D}��$ molecular state. With the possible quantum numbers $J^p=1/2^{\pm}$ and $3/2^{\pm}$, the partial decay widths of the $\bar{D}��-\bar{D}��$ molecular state into the $��_c^{+}K^{-}$, $��_c^{+}K^{-}$,and $��_c^{+}��^{-}$ final states through hadronic loop are calculated with the help of the effective Lagrangians. By comparison with the LHCb observation, the current results of total decay width support the $��(2923)^0$ as $\bar{D}��-\bar{D}��$ molecule while the decay width of the $��_c(2938)^0$ and $��(2964)^0$ can not be well reproduced in the molecular state picture. In addition, the calculated partial decay widths with $S$ wave $\bar{D}��-\bar{D}��$ molecular state picture indicate that allowed decay modes, $��_c^{+}��^{-}$, may have the biggest branching ratios for the $��_c(2923)$. The experimental measurements for this strong decay process could be a crucial test for the molecule interpretation of the $��_c(2923)$., arXiv admin note: text overlap with arXiv:1002.0218 by other authors