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 F 2 in the Endpoint overlap Model. We find the model correctly reproduces the scaling of the ratio of F 2 with the Dirac form factor F 1 observed at the Jefferson Laboratory. The calculation uses the leadingpower, leading-twist Dirac structure of the quark light-cone wave function and the same endpoint dependence previously determined from the Dirac form factor F 1 . There are no parameters and no adjustable functions in the Endpoint Model's prediction for the scaling behavior of F 2 . The model's predicted momentum dependence of the ratio F 2 (Q 2 )/F 1 (Q 2 ) 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.

The Status and Future of Color Transparency and Nuclear Filtering

“…This rule is predicted by the hard scattering mechanism [24], but not observed in data. It also naturally leads to the prediction, F 2 /F 1 ∝ 1/Q [25], in agreement with data, while the short distance model would predict F 2 /F 1 ∝ 1/Q 2 . Furthermore, it does not predict the phenomenon of color transparency, at least in its simplest form, and hence is nicely consistent with experimental results [8][9][10][11][12].…”

Transition distribution amplitudes and hard exclusive reactions with baryon number transfer

“…[4]). The importance of the Sudakov suppression of some delicate integration regions was in particular discovered [48], which in turn may help to understand the suppression of endpoint region contributions for meson and baryon form factors [49,50] (for an alternative point of view, see [51,52]). Moreover, the absence of pinch singularities, which is a necessary element of the proof of factorization, was shown in [53] for the scattering amplitude for electroproduction processes at fixed angle, putting on a firm ground the collinear factorized framework for various processes.…”

Compton scattering in the Endpoint Model

“…In the above diagrams, the incoming proton is understood to be deflected by q µ = (0, Q, 0, 0), where q µ = q µ 1 − q µ 2 . This allows us to use the same frame and kinematics for the proton, as was used for the analysis of Dirac and Pauli form factors [14,15] with q = (0, Q, 0, 0), P = ( Q 2 /2 + M 2 P , −Q/2, 0, Q/2), P = ( Q 2 /2 + M 2 P , Q/2, 0, Q/2). We can choose q 1 , q 2 appropriately so that θ cm ∈ [64 • , 130 • ], which is the range of the data obtained at Jlab [3].…”

“…In the above diagrams, the incoming proton is understood to be deflected by q µ = (0, Q, 0, 0), where q µ = q µ 1 − q µ 2 . This allows us to use the same frame and kinematics for the proton, as was used for the analysis of Dirac and Pauli form factors [14,15] with q = (0, Q, 0, 0),…”

“…The Endpoint Model [14,15] applies to all exclusive hadronic processes and reproduces the quark counting rules at high energies. In the model, the dominant contributions involve struck quarks carrying a large fraction of the hadron's momenta.…”