Photondark photon conversions in extreme background electromagnetic fields
Abstract
The mixing of photons with light pseudoscalars in the presence of external electromagnetic fields has been used extensively to search for axionlikeparticles. A similar effect for dark photon propagating states is usually not considered due to the LandauYang theorem. We point out that mixing between photon and dark photon propagating states in background electromagnetic fields can indeed occur, in nonlinear QED, through a fourphoton vertex by integrating out the electron box diagram. Starting from the Schwinger Lagrangian, we derive the equations of motion for dark photons interacting with the Standard Model photon through gauge kinetic terms. We provide expressions for the perpendicular and parallel refractive indices in series expansions in the critical field strength, valid both in the strong and weak background field limits. We then consider mixing between the photondark photon propagating system in the presence of pure electric and magnetic background fields, and work out the probability of conversion when the background fields are homogeneous. We indicate outlines of the calculation in the inhomogeneous case, and finally express our results in the activesterile basis, where we find that the mixing induced by background fields can lead to corrections to the treelevel mixing in the zero field limit that is usually considered to probe such systems. Our results may find applications for probing photondark photon conversions in the vicinity of neutron stars and in tabletop petawatt laser experiments.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 November 2019
 DOI:
 10.1088/14757516/2019/11/020
 arXiv:
 arXiv:1904.08968
 Bibcode:
 2019JCAP...11..020F
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 1+16 pages, added references, probability of conversion given in physical basis, conclusions unchanged