Local nuclear slope and curvature in high energy pp and bar pp elastic scattering

The local nuclear slope $B(s,t) = {d \over d t} (\ln {d\sigma_n (s,t)\over dt})$ is reconstructed from the experimental angular distributions with a procedure that uses overlapping $t$-bins, for an energy that ranges from the ISR to the $S\bar ppS$ and the Tevatron. Predictions of several models of ($p,p$) and ($\bar p,p$) elastic scattering at high energy are tested in $B(s,t)$ at small $|t|$. Only a model with two-components Pomeron and Odderon gives a satisfactory agreement with the (non fitted) slope data, in particular for the evolution of $B(s,t)$ with $s$ as a function of $t$ in $\bar pp$ scattering. This model predicts a similar behavior for $pp$ and $\bar pp$ scattering at small $|t|$. A detailed confirmation for $pp$ collisions would be expected from RHIC.