Observation of a Narrow Resonance of Mass 2.46 GeV/c² in the Dₛ*+π⁰ Final State, and Confirmation of the DₛJ*(2317)

Original · EN

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 Dₛ*π⁰ final state, with a mass near 2.46 GeV/c². The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV/c², the DsJ*(2317)+, that decays to Dₛπ⁰. Reconstructing the Dₛπ⁰ and Dₛ*π⁰ final states in CLEO data, we observe a peak in each of the corresponding reconstructed mass difference distributions, ΔMDₛπ₀ = M(Dₛπ⁰) - M(Dₛ) and ΔMDₛ*π₀ = M(Dₛ*π⁰) - M(Dₛ*), both of them at values around 350 MeV/c². These peaks constitute statistically significant evidence for two distinct states, at 2.32 and 2.46 GeV/c², 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 ΔMDₛπ₀ = 350.4 ± 1.2[stat.] ± 1.0 [syst.] MeV/c² for the DsJ*(2317)+ state, and ΔMDₛ*π₀ = 351.6 ± 1.7[stat.] ± 1.0 [syst.] MeV/c² for the new state at 2.46 GeV/c². We have also searched, but find no evidence, for decays of DsJ*(2317) into the alternate final states Dₛ*γ, Dₛγ, and Dₛπ+π-. The observations of the two states at 2.32 and 2.46 GeV/c², in the Dₛπ⁰ and Dₛ*π⁰ decay channels respectively, are consistent with their possible interpretations as c s-bar mesons with orbital angular momentum L=1, and spin-parity Jᵖ = 0+ and 1+.