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Pair term in the Electromagnetic Current within the Front-Form Dynamics: Spin-0 Case

J. P. B. C. de Melo·T. Frederico·E. Pace·G. Salme`
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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)$^2$. A comparison with results obtained within the Front-Form Hamiltonian dynamics with a fixed number of constituents is also presented.

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J. P. B. C. de Melo, T. Frederico, E. Pace, G. Salme`. 2002-05-02. Pair term in the Electromagnetic Current within the Front-Form Dynamics: Spin-0 Case. https://doi.org/10.1016/s0375-9474(02)00990-9

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