Large-distance effects on spin observables at RHIC

The impact of large-distance contributions on the behaviour of the slopes of the spin-non-flip and of the spin-flip amplitudes is analysed. It is shown that the long tail of the hadron potential in impact parameter space leads to a larger value of the slope for the spin-flip amplitude (without the kinematic factor sqrt(|t|)) than for the spin-non-flip amplitude. This effect is taken into account in the calculation of the analysing power in proton-nucleus reactions at high energies.