A new method for the determination of the real part of the hadron elastic scattering amplitude at small angles and high energies [rapid communication]

A new method for the determination of the real part of the elastic scattering amplitude is examined for high energy proton-proton at small momentum transfer. This method allows us to decrease the number of model assumptions, to obtain the real part in a narrow region of momentum transfer and to test different models. The real part is computed at a given point t_min near t = 0 from the known Coulomb amplitude. Hence one obtains an important constraint on the real part of the forward scattering amplitude and therefore on the ρ-parameter (measuring the ratio of the real to imaginary part of the scattering amplitude at t = 0), which can be tested at LHC.