Pair term in the Electromagnetic Current within the Front-Form Dynamics: Spin-0 Case
Abstract
The frame and scale dependence of the pair-term contribution to the electromagnetic form factor of a spin-zero composite system of two-fermions is studied within the Light Front. The form factor is evaluated from the plus-component of the current in the Breit frame, using for the first time a nonconstant, symmetric ansatz for the Bethe-Salpeter amplitude. The frame dependence is analyzed by allowing a nonvanishing plus component of the momentum transfer, while the dynamical scale is set by the masses of the constituents and by mass and size of the composite system. A transverse momentum distribution, associated with the Bethe-Salpeter amplitude, is introduced which allows to define strongly and weakly relativistic systems. In particular, for strongly relativistic systems, the pair term vanishes for the Drell-Yan condition, while is dominant for momentum transfer along the light-front direction. For a weakly relativistic system, fitted to the deuteron scale, the pair term is negligible up to momentum transfers of 1(GeV/c). A comparison with results obtained within the Front-Form Hamiltonian dynamics with a fixed number of constituents is also presented.
Keywords
Cite
@article{arxiv.nucl-th/0205010,
title = {Pair term in the Electromagnetic Current within the Front-Form Dynamics: Spin-0 Case},
author = {J. P. B. C. de Melo and T. Frederico and E. Pace and G. Salme`},
journal= {arXiv preprint arXiv:nucl-th/0205010},
year = {2009}
}
Comments
25 pages + 7 figures; axodraw.sty included. To appear in Nucl. Phys. A