Decay constants of the two-pole $D_0^*(2300)$

Abstract

The nature of the scalar charmed meson $D_0^*(2300)$ remains one of the most intriguing states in hadron spectroscopy. A prominent interpretation is a two-pole structure generated by the coupled channels $Dπ$, $Dη$, $D_s\bar K$, and $Dη'$, in which the lower pole couples mainly to $Dπ$ and the higher pole to $D_s\bar K$. Following this picture, we calculate the decay constants of these two poles using the effective Lagrangian approach. The resulting values, $f_{D_0^*}^{(\mathrm{lower})}=64.6^{+0.9}_{-1.0}\,\mathrm{MeV}$ and $f_{D_0^*}^{(\mathrm{higher})}=80.8^{+9.6}_{-5.3}\,\mathrm{MeV}$, are substantially smaller than those predicted by conventional $c\bar q$ excited-state scenarios. This difference suggests that decay constants can serve as a sensitive probe to discriminate between different internal structures of the $D_0^*(2300)$. As a phenomenological application, we further predict the branching fractions for the Cabibbo-favored decays $B_s \to D_s D_0^*$, $Λ_b \to Λ_c D_0^*$, and $Ξ_b \to Ξ_c D_0^*$ within the factorization approach. These predictions provide crucial tests to validate the two-pole interpretation of the $D_0^*(2300)$.