Possible explanations of the observed $\Lambda_c$ resonances

Abstract

Inspired by the latest experimental progress, we systematically study the OZI-allowed two-body strong decay properties of $1P$-, $1D$-, $2S$- and $2P$-wave $\Lambda_c$ baryons within the $j $-$j$ coupling scheme in the framework of the quark pair creation model. The calculations indicate that: (i) Taking the observed states $\Lambda_c(2595)^+$ and $\Lambda_c(2625)^+$ as the $1P$-wave $\lambda$-modes states $\Lambda_c|J^P=1/2^-,1\rangle_{\lambda}$ and $\Lambda_c|J^P=3/2^-,1\rangle_{\lambda}$, respectively, we can reproduce the experimental data well in theory. (ii) Combining with the measured mass and the decay properties of $\Lambda_c(2860)^+$, this excited state can be explained as $1D$-wave $\lambda$-mode state $\Lambda_c|J^P=3/2^+,1\rangle_{\lambda\lambda}$. (iii) The newly observed state $\Lambda_c(2910)^+$ may be assigned as one of the $1P$-wave $\rho$-mode states $\Lambda_c|J^P=3/2^-,2\rangle_{\rho}$ or $\Lambda_c|J^P=5/2^-,2\rangle_{\rho}$. Meanwhile, we notice that the partial decay width ratio between $\Sigma_c\pi$ and $\Sigma_c^*\pi$ for the two candidates is significantly different. Hence, experimental progress in this ratio measurement may shed light on the nature of $\Lambda_c(2910)^+$. (iv) According to the properties of $\Lambda_c(2765)^+$, we find that the $2S$-wave $\lambda$-mode state $\Lambda_{c1}|J^P=1/2^+,0\rangle_{\lambda}$ may be a potential candidate. (v) The $2P$-wave $\lambda$-mode state $\Lambda_{c1}|J^P=3/2^-,1\rangle_{\lambda}$ is mostly likely to be a good assignment of the controversial state $\Lambda_c(2940)^+$. Both the total decay width and partial decay ratio between $pD^0$ and $\Sigma_c\pi$ are in good agreement with the observations. (vi) In addition, for the missing $\Lambda_c$ excitations, we obtain their strong decay properties and hope that's useful for future experimental exploration.