Low-energy universality and the new charmonium resonance at 3870 MeV

The recently discovered narrow charmonium resonance near 3870 MeV is interpreted as a hadronic molecule whose constituents are the charm mesons D-0 and (D) over bar*(0) or (D) over bar (0) and D*(0). Because of an accidental fine-tuning of the molecule to very near the D-0(D) over bar*(0) threshold, it has some universal properties that are completely determined by the unnaturally large D-0(D) over bar*(0) scattering length a. Its narrow width can be explained by the suppression by a factor of 1/a of decay modes other than the decay of a constituent (S) over bar*(0) or D*(0). Its production rates are also suppressed by a factor of 1/a. A particularly predictive mechanism for generating the large scattering length is the accidental fine-tuning of a P-wave charmonium state to the D-0(D) over bar*(0) threshold.