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First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+

The SELEX Collaboration·A. V. Evdokimov
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Abstract

We report the first observation of a charm-strange meson DsJ(2632) at a mass of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9 MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2 at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta) is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the Ds eta decay mode.

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The SELEX Collaboration, A. V. Evdokimov. 2004-10-30. First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+. https://doi.org/10.1103/physrevlett.93.242001

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