$\eta_{c}\rightarrow l^{+}l^{-}$ and $\chi_{c0}\rightarrow l^{+}l^{-}$   decays revisited
  We present a calculation of $\eta_{c}\rightarrow l^{+}l^{-}$ and $\chi_{c0}\rightarrow l^{+}l^{-}$ decay widths. The amplitudes are computed within leading-order approximation using NRQCD framework. Numerical results for the branchings fractions are presented. 
N. Kivel and A. Kupsc
hep-ph