The Dirac form factor predicts the Pauli form factor in the Endpoint Model

Abstract

We compute the momentum-transfer dependence of the proton Pauli form factor 𝐹2 in the Endpoint overlap Model. We find the model correctly reproduces the scaling of the ratio of 𝐹2 with the Dirac form factor 𝐹1 observed at the Jefferson Laboratory. The calculation uses the leading-power, leading-twist Dirac structure of the quark light-cone wave function and the same endpoint dependence previously determined from the Dirac form factor 𝐹1. There are no parameters and no adjustable functions in the Endpoint Model’s prediction for the scaling behavior of 𝐹2. The model’s predicted momentum dependence of the ratio 𝐹2(𝑄2) 𝐹1(𝑄2) is quite insensitive to the endpoint wave function, which explains why the observed ratio scales like 1 / Q down to rather low momentum transfers. We also fit the magnitude of this ratio by adjusting the parameters of the wave function. The Endpoint Model appears to be the only comprehensive model consistent with all form factor information as well as reproducing fixed-angle proton–proton scattering at large momentum transfer. Any one of the processes is capable of predicting the others.