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Journal Articles European Physical Journal A Year : 2004

Form factors in the 'point form' of relativistic quantum mechanics : single and two-particle currents

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Abstract

Electromagnetic and Lorentz-scalar form factors are calculated for a bound system of two spin-less particles exchanging a zero-mass scalar particle. Different approaches are considered including solutions of a Bethe-Salpeter equation, a ``point form'' approach to relativistic quantum mechanics and a non-relativistic one. The comparison of the Bethe-Salpeter results, which play the role of an ``experiment'' here, with the ones obtained in ``point form'' in single-particle approximation, evidences sizable discrepancies, pointing to large contributions from two-body currents in the latter approach. These ones are constructed using two constraints: ensuring current conservation and reproducing the Born amplitude. The two-body currents so obtained are qualitatively very different from standard ones. Quantitatively, they turn out not to be sufficient to remedy all the shortcomings of the ``point form'' form factors evidenced in impulse approximation.

Dates and versions

in2p3-00022163 , version 1 (24-08-2004)

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B. Desplanques, L. Theussl. Form factors in the 'point form' of relativistic quantum mechanics : single and two-particle currents. European Physical Journal A, 2004, 21, pp.93-116. ⟨10.1140/epja/i2003-10183-2⟩. ⟨in2p3-00022163⟩
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