Properties of QQ̅ mesons in nonrelativistic QCD formalism

The decay rates of QQ̅ mesons (Q ɛ c, b) are studied in the nonrelativistic quantum chromodynamics (QCD) formalism in terms of their short-distance and long-distance coefficients. The long-distance coefficients are obtained through phenomenological potential model description of the mesons. The model parameters that reproduces the mass spectrum of the cc̅ , bb̅ , and cb̅ mesons are employed to study the decay widths of these mesons. We extract the mass spectrum and the respective radial wave functions from the different potential models as well as from a nonrelativistic phenomenological quark-antiquark potential of the type V(r)=-α_c/r+Ar^ν, with ν varying from 0.5 to 2. The spin hyperfine and spin-orbit interactions are employed to obtain the masses of the pseudoscalar and vector mesons. The decay constants with QCD corrections are computed in this model as well as in the case of other potential models for comparison. The digamma and dileptonic decays of cc̅ and bb̅ mesons are investigated using some of the known potential models without and with radiative corrections up to the lowest order. These decay width are also computed within the nonrelativistic QCD formalism up to O(v⁴) by making uses of the respective spectroscopic parameters of the models. Our theoretical predictions of the decays of the cc̅ and bb̅ mesons and the results obtained from some of the other potential schemes are compared with the experimental values. The partial widths and lifetime of the B_c meson are also computed using the model parameters and are found to be in good accordance with the experimental values.