Zeros, dips, and signs in pp and p(p)over-bar elastic amplitudes - art. no. 077507

The dips observed in the differential cross sections of elastic pp and p (p ) over bar scattering are studied in terms of the locations of the zeros of the real and imaginary parts of the amplitude and of the sign of real pari at large \t\. It is confirmed that the differences in shapes of the dips i n the pp and p (p) over bar systems are determined by a change of sign of t he real tail, which seems to be determined by perturbative QCD contribution s.