The interplay of hadronic amplitudes and Coulomb phase in LHC measurements at 13 TeV

Detailed analysis of the measurements of differential cross sections in the forward region of pp elastic scattering at 13 TeV in LHC is performed. The structures of the real and imaginary parts of the scattering amplitude are investigated, both requiring exponential and linear factors. Representations of the data in different conditions are compared, investigating the role of the Coulomb-nuclear interference and satisfying predictions from dispersion relations. The additivity of nuclear and Coulomb eikonal phases to determine the interference phase in pp scattering is submitted to a comparison with assumption of phase equal to zero. The structures of the real part of the scattering amplitude under the two assumptions are examined, and direct comparison is performed with the information extracted from the data. The alternative criteria for the treatment of the interference phase lead to different values for the ρ parameter between 0.1 and 0.13 while σ differ by 0.18 mb, and it is shown that the available data cannot discriminate the two choices. As an alternative study, we also present the results for the amplitude parameters and χ2 values when constant values of 2 and 3 radians are subtracted from the analytical expression for the interference phase. Keywords: Elastic scattering, Coulomb interference, Hadronic amplitude