Abstract
The specific features of nonlinear pair production and radiation processes in an ultratsrong rotating electric field are investigated, taking into account that this field models the antinodes of counterpropagating laser beams. It is shown that a particle in a rotating electric field acquires an effective mass which depends on its momentum absolute value as well as on its direction with respect to the field plane. This phenomenon has an impact on the nonlinear Breit-Wheeler and nonlinear Compton processes. The spectra of the produced pairs in the first case, and the emitted photon in the second case, are shown to bear signatures of the effective mass. In the first case, the threshold for pair production by a $\gamma$-photon in the presence of this field varies according to the photon propagation direction. In the second case, varying the energy of the incoming electron allows for the measurement of the momentum dependence of the effective mass. Two corresponding experimental setups are suggested.
Highlights
The modification of a particle mass due to an interaction with a strong field is a fundamental phenomenon, appearing in a variety of fields in physics
The effective mass in the presence of a rotating electric field (REF) was investigated in detail
It was shown to depend on the field amplitude and on the particle momentum and propagation direction. The influence of this effect on the probabilities of the nonlinear Breit-Wheeler (NLBW) and nonlinear Compton (NLC) scatterings was explored by employing the Baier-Katkov semiclassical formalism
Summary
The modification of a particle mass due to an interaction with a strong field is a fundamental phenomenon, appearing in a variety of fields in physics. The potential experienced by the particle is periodic and one could expect that the effectivemass features would resemble the condensed-matter case, inducing a complex dispersion relationship for the dressed electron. The example of a rotating electric field (REF) is employed to show that for external fields deviating from the PWF, a momentum-dependent effective mass may arise. The min√imal value of m∗, corresponding to ξ 1, is m∗ ≈ m∗P/ 2 In this limit, the local crossed-field approximation sets in for the NLC and NLBW processes, when the probabilities and spectra depend solely on the parameter χ , but not on ξ , and all signatures of the effective mass vanish.
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