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arXiv · 2008.10691

Energy of a point-like neutron in an external electromagnetic field

Jesus Saenz·Michael Engelhardt·Roman Höllwieser
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Abstract

A point-like neutron in an external electromagnetic field experiences a shift in energy that mimicks the effect of an actual structural deformation of an extended neutron, i.e., a proper polarizability. In order to be able to differentiate between the former and the latter, a Foldy-Wouthuysen transformation is constructed which yields the energy shift of a point-like neutron quadratic in the external field in a derivative expansion, generalizing a long-known result for the dipole electric polarizability due to Foldy. The ten leading Foldy contributions to the energy are determined for a zero-momentum neutron. In addition, eliminating the momentum operator in favor of the velocity operator, analogous results are derived for a zero-velocity neutron. In this case, operator ordering ambiguities are encountered that permit only a determination of eight of the ten Foldy terms.

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Jesus Saenz, Michael Engelhardt, Roman Höllwieser. 2020-08-24. Energy of a point-like neutron in an external electromagnetic field. https://doi.org/10.1103/physrevd.104.056002

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