J/ -Nucleon Scattering Length and In-Medium Mass Shift of J/  in QCD Sum Rule Analysis

We calculate the spin-averaged J/ψ-nucleon scattering length aJ/ψ by directly applying the QCD sum rule to the J/ψ-N forward scattering amplitude. Our result, aJ/ψ = −0.10 ±0.02 fm, implies the possibility of bound states with nuclei, though the force is weaker than that of the light vector mesons (ρ,ω,ϕ)-N cases. Up to dimension-4 gluonic operators, we evaluate the scattering length with a twist-2 contribution. This increases the absolute value of the scattering length by about 30%. if we apply aJ/ψ to the effective mass of J/ψ in nuclear matter on the basis of the linear density approximation, it exhibits very slight decrease (4–7 MeV) at normal matter density.