Up and down the Riemann surfaces of the baryon form factors

The recent measurement of the modulus and phase of the ratio G(E)(Lambda)/G(M)(Lambda), between the electric and the magnetic Lambda form factors, performed by the BESIII experiment, offers the unique possibility of exploring for the first time ever the complex structure of this form factor ratio. The investigation is made possible by a dispersive procedure based on analyticity and a set of first-principle constraints, that is defined ad hoc.