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Recently, many unexpected new particles were discovered with masses around 4 GeV/c2. They are collectively called XYΖ mesons and while some of them have been identified as charmonium states, many others have properties that don't fit into the quark-antiquark classification, and so far remain unclassified. The X(3872) meson was the first to be discovered and is the most studied of these states, and there is a variety of hypotheses on its nature. Other new states include the X(3940) and Y (3940) mesons, which have the same mass and similar widths; it is not clear if they are the same state or not. More experimental evidence is required to understand these particles. We report a search for B → X(3872)K with X(3872) decaying to D0 D0 using a sample of 657 million BB pairs recorded at the γ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The study is performed for both D0 → D0γ and D0 → D0π0 decay modes. We find a total signal of 50.1 events with a mass of 3872.9 MeV/c2, a width of 3.9 MeV/c2 and a product branching fraction Ɓ(B→ X(3872)Κ) × Ɓ(X(3872) → D0 D0) = (0.80 ± 0.20 ± 0.11) × 10-4. The statistical significance of the signal is 7.9σ. Furthermore, from the same study we also set an upper limit at 90% confidence level on the product branching fraction Ɓ(B→ Y(3940)K) × Ɓ(Y (3940) → D*0 D0) < 0.67 × 10-4 which suggests that the X(3940) and Y (3940) mesons are different states.
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Tagir Aushev, Sun Hee Kim, Donghyun Kim, Jing Li
Tagir Aushev, Aurelio Bay, Sun Hee Kim, Sanjeev Kumar, Jing Li
Tagir Aushev, Vladislav Balagura, Aurelio Bay, Stewart Cole, Sun Hee Kim, Ji Hyun Kim, Jing Li