Impact of new particles on the ratio of electromagnetic form factors

We consider the electromagnetic form factors ratios in the Rosenbluth and polarization methods. We explore what impact adding new particles as mediators in electron-proton scattering has on these ratios. We show that such new particles can compensate for the difference between the two methods and potentially solve this paradox. Consequently, we find some bounds on the scalar coupling as alpha sc similar to 10-5 for msc similar to 5 MeV-2 GeV and alpha sc similar to 10-4 - 10-3 for msc similar to 2-10 GeV. Meanwhile, the vector coupling is bounded as alpha v similar to 10-5 for mv similar to 5 MeV-1.1 GeV and alpha v similar to 10-4 - 10-3 for mv similar to 1.2-10 GeV. These constraints are in complete agreement with those found in other independent terrestrial experiments.