Impact of new particles on the ratio of electromagnetic form factors

Abstract 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 α sc ∼ 10 −5 for m sc ∼ 5 MeV–2 GeV and α sc ∼ 10 −4 − 10 −3 for m sc ∼ 2–10 GeV. Meanwhile, the vector coupling is bounded as α v ∼ 10 −5 for m v ∼ 5 MeV–1.1 GeV and α v ∼ 10 −4 − 10 −3 for m v ∼ 1.2–10 GeV. These constraints are in complete agreement with those found in other independent terrestrial experiments.