Is $D_{sJ}^{+}(2632)$ the first radial excitation of $D_s^{\ast }(2112)$?

Abstract

We present a quantitative analysis of the $D_{sJ}^{+}(2632)$ observed by SELEX mainly focusing on the assumption that $D_{sJ}^{+}(2632)$ is the first radial excitation of the $1^{-}$ ground state $D_s^{\ast }(2112)$. By solving the instantaneous Bethe-Salpeter equation, we obtain the mass $2658\pm 15$ MeV for the first excited state, which is about 26 MeV heavier than the experimental value $2632\pm 1.7$ MeV. By means of PCAC and low-energy theorem we calculate the transition matrix elements and obtain the decay widths: $\Gamma (D_{sJ}^{+}\to D_s^{+}\eta )=4.07\pm 0.34$ MeV, $\Gamma (D_{sJ}^{+}\to D^0{K}^{+})\simeq \Gamma (\Gamma (D_{sJ}^{+}\to D^{+}{K}^0)=8.9\pm 1.2$ MeV, and the ratio $\Gamma (D_{sJ}^{+}\to D^0{K}^{+})/\Gamma (D_{sJ}^{+}\to D_s^{+}\eta )=2.2\pm 0.2$ as well. This ratio is quite different from the SELEX data $0.14\pm 0.06$. The summed decay width of those three channels is approximately 21.7 MeV, already larger than the observed bound for the full width ($\le 17$ MeV). Furthermore, assuming $D_{sJ}^{+}(2632)$ is $1^{-}$ state, we also explore the possibility of $S-D$ wave mixing to explain the SELEX observation. Based on our analysis, we suspect that it is too early to conclude that $D_{sJ}^{+}(2632)$ is the first radial excitation of the $1^{-}$ ground state $D_s^{\ast }(2112)$. More precise measurements of the relative ratios and the total decay width are urgently required especially for $S-D$ wave mixing.

Comments: 12 pages, 8 figures