QCD Sum Rules for  ,  ,   Meson-Nucleon Scattering Lengths and the Mass Shifts in Nuclear Medium

A new QCD sum rule analysis on the spin-isospin averaged ρ, ω and ϕ meson-nucleon scattering lengths is presented. By introducing the constraint relation on the low energy limit of the vector-current nucleon forward scattering amplitude (low energy theorem), we obtain aρ = −0.47±0.05 fm, aω = −0.41±0.05 fm and aϕ = −0.15±0.02 fm, which suggests that these V-N interactions are attractive. It is also proved that previous studies on the mass shift of these vector mesons in the nuclear medium are essentially those obtained from these scattering lengths in the linear density approximation.