The rho parameter of low energy proton-antiproton scattering in the 3P0 quark model

The real-to-imaginary ratio ϱ of the proton-antiproton forward elastic scattering amplitude is analyzed in a nucleon-antinucleon (NN) potential model. The annihilation part of the NN interaction is based on a constituent quark model applying the effective 3P0 quark-antiquark operator together with a planar quark diagram topology. The elastic interaction is the G-parity transform of meson exchange NN interactions as defined by the Bonn and Paris potentials. The momentum dependence of the ϱ parameter can be well reproduced for plab > 250 MeV/c, but despite strong variations in the parameterization of the annihilation part no pronounced bump structure for ϱ at low momenta as suggested by experiment can be found.