X (3915) as a Ds D ¯ s bound state X (3915) AS A Ds D ¯ s BOUND STATE XIN LI and M.B. VOLOSHIN

We suggest that the observed properties of the charmonium-like resonance X(3915) can possibly be explained if it is an S-wave molecular bound state of the DsD¯s meson pair with a binding energy of about 18 MeV. In particular, the decays of X(3915) to pairs of nonstrange D mesons are suppressed and proceed at a rate comparable to that of the decay X(3915)→ωJ/ψ, whose branching fraction can be as large as about 0.3. Other major types of decay of X(3915) with a comparable (or slightly smaller) rate are the transition X(3915)→ηηc and the decays into light hadrons due to the annihilation of the cc¯ quark pair. The existence of a bound state should lead to an enhancement in the spectrum of the invariant mass for the DsD¯s near threshold in B decays, e.g. in B→KDsD¯s the enhancement of which can be tested experimentally.