Possible 2S and 1D charmed and charmed-strange mesons
  Possible $2S$ and $1D$ excited $D$ and $D_s$ states are studied, the charmed states $D(2550)^0$, $D^\ast(2600)$, $D(2750)^0$ and $D^\ast(2760)$ newly observed by the BaBar Collaboration are analyzed. The masses of these states are explored within the Regge trajectory phenomenology, and the strong decay widths are computed through the method proposed by Eichten {\it et al.}\cite{Eichten}. Both the mass and the decay width indicate that $D(2550)^0$ is a good candidate of $2^1S_0$. $D^\ast(2600)$ and $D_{s1}^\ast(2700)^\pm$ are very possible the admixtures of $2^3S_1$ and $1^3D_1$ with $J^P=1^-$ and a mixing angle $\phi\approx 19^0$. $D^\ast(2760)$ and $D_{sJ}^\ast(2860)^\pm$ are possible the $1^3D_3$ $D$ and $D_s$, respectively. $D(2750)^0$ and $D^\ast(2760)$ seem two different states, and $D(2750)^0$ is very possible the $1D(2^-, \frac{5}{2})$ though the possibility of $1D(2^-, \frac{3}{2})$ has not been excluded. There may exist an unobserved meson $D_{sJ}(2850)^\pm$ corresponding to $D^\ast_{sJ}(2860)^\pm$. 
Bing Chen, Ling Yuan and Ailin Zhang
hep-ph hep-ex