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Observation of a Narrow Resonance of Mass 2.46 GeV/c^2 in the D_s^*+π^0 Final State, and Confirmation of the D_sJ^*(2317)

Using 13.5 fb^{-1} of e^+e^- annihilation data collected with the CLEO-II detector, we have observed a new narrow resonance in the D_s^*π^0 final state, with a mass near 2.46 GeV/c^2. The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV/c^2, the D_{sJ}^*(2317)^+, that decays to D_sπ^0. Reconstructing the D_sπ^0 and D_s^*π^0 final states in CLEO data, we observe a peak in each of the corresponding reconstructed mass difference distributions, ΔM_{D_sπ^0} = M(D_sπ^0) - M(D_s) and ΔM_{D_s^*π^0} = M(D_s^*π^0) - M(D_s^*), both of them at values around 350 MeV/c^2. These peaks constitute statistically significant evidence for two distinct states, at 2.32 and 2.46 GeV/c^2, taking into account the background source that each state comprises for the other in light of the nearly identical values of ΔM observed for the two peaks. We have measured the mean mass differences ΔM_{D_sπ^0} = 350.4 \pm 1.2[stat.] \pm 1.0 [syst.] MeV/c^2 for the $D_{sJ}^*(2317)^+$ state, and ΔM_{D_s^*π^0} = 351.6 \pm 1.7[stat.] \pm 1.0 [syst.] MeV/c^2 for the new state at 2.46 GeV/c^2. We have also searched, but find no evidence, for decays of D_{sJ}^*(2317) into the alternate final states D_s^*γ, D_sγ, and D_sπ^+π^-. The observations of the two states at 2.32 and 2.46 GeV/c^2, in the D_sπ^0 and D_s^*π^0 decay channels respectively, are consistent with their possible interpretations as c s-bar mesons with orbital angular momentum L=1, and spin-parity J^P = 0^+ and 1^+.