QCD sum rules for J/psi in the nuclear medium: calculation of the Wilson   coefficients of gluon operators up to dimension 6
  We calculate the Wilson coefficients of all dimension 6 gluon operators with non zero spin in the correlation function between two heavy vector currents. For the twist-4 part, we first identify the three independent gluon operators, and then proceed with the calculation of the Wilson coefficients using the fixed point gauge. Together with the previous calculation of the Wilson coefficients for the dimension 6 scalar gluon operators by Nikolaev and Radyushkin, our result completes the list of all the Wilson coefficients of dimension 6 gluon operators in the correlation function between heavy vector currents. We apply our results to investigate the mass of $J/\psi$ in nuclear matter using QCD sum rules. Using an upper bound estimate on the matrix elements of the dimension 6 gluon operators to linear order in density, we find that the density dependent contribution from dimension 6 operators is less than 40% of the dimension 4 operators with opposite sign. The final result gives about -4 MeV mass shift for the charmonium at rest in nuclear matter. 
Sungsik Kim and Su Houng Lee (Yonsei University)