Probing the Pomeron spin-flip with Coulomb-nuclear interference

Brand-new high-precision data for single-spin asymmetry $A_N(t)$ in small angle elastic $pp$ scattering from the fixed target experiment HJET at BNL at $E_{lab}=100$ and $255$ GeV, as well as high energy STAR measurements at $\sqrt{s}=200$ GeV, for the first time allowed to determine the spin-flip to non-flip ratio $r_5(t)$ in a wide energy range. We introduced essential modification in the Coulomb-nuclear interference (CNI) mechanism, missed in previous analyses. In particular, absorptive corrections make the proton electromagnetic vertex different from the formfactor, measured in electron-proton scattering. Introduction of absorptive corrections strongly affect the results for $r_5(t)$. The Regge analysis allowed to single out the Pomeron contribution to the spin-flip amplitude, which steeply rises with energy. We found the spin-flip to non-flip ratio of the Pomeron amplitudes to be nearly $-10\%$, rising with energy as $s^{0.34}$, both in good accord with theoretical expectations.