# Form factors in relativistic quantum mechanics: constraints from space-time translations

Abstract : The comparison of form factors calculated from a single-particle current in different relativistic quantum mechanic approaches evidences tremendous discrepancies. The role of constraints co\-ming from space-time translations is considered here with this respect. It is known that invariance under these translations implies the energy-momentum conservation relation that is usually assumed to hold globally. Transformations of the current under these translations, which lead to this result, also imply constraints that have been ignored so far in relativistic quantum mechanic approaches. An implementation of these constraints is discussed in the case of a model with two scalar constituents. It amounts to incorporate selected two-body currents to all orders in the interaction. Discrepancies for form factors in different approaches can thus be removed, contributing to restore the equivalence of different approaches. Results for the standard front-form approach ($q^+=0$) are found to fulfill the constraints and are therefore unchanged. The relation with results from a dispersion-relation approach is also made.
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Conference papers
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Cited literature [8 references]

http://hal.in2p3.fr/in2p3-00298980
Contributor : Emmanuelle Vernay <>
Submitted on : Tuesday, October 14, 2008 - 10:19:32 AM
Last modification on : Thursday, November 19, 2020 - 12:58:51 PM
Long-term archiving on: : Monday, May 31, 2010 - 6:18:13 PM

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• HAL Id : in2p3-00298980, version 1
• ARXIV : 0810.2386

### Citation

B. Desplanques, Y.B. Dong. Form factors in relativistic quantum mechanics: constraints from space-time translations. Light Cone 2008. Relativistic Nuclear and Particle Physics, Jul 2008, Mulhouse, France. pp.018. ⟨in2p3-00298980⟩

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