Field-assisted polarization-changing Compton scattering

Abstract Motivated by experimental initiatives such as the Helmholtz International Beamline for Extreme Fields, we study Compton scattering of x-rays at electrons in a strong external field (e.g. a strong optical laser) with special emphasis on the polarization-changing contribution on the amplitude level. Apart from advancing our theoretical understanding, the goal of this study is two-fold. On the one hand, Compton scattering is a potential background process for the planned vacuum birefringence experiments. On the other hand, this effect could be used for diagnostic purposes. Since the polarization-changing signal from free electrons (i.e. without the external field) vanishes in forward direction, the ratio of the polarization-changing and the normal (polarization conserving) contribution yields information about the field strength at the interaction point.