Analysis of the geometric effect on laser-assisted decay processes

Choosing a specific direction for the propagation of laser field waves often presents a challenge for researchers studying laser-assisted ultrafast quantum processes. They are faced with the question of why exactly this direction and not another. This paper resolves the discussion in this issue regarding decay processes. Therefore, we study theoretically the pion decay process in the presence of a circularly polarized laser field propagating along an arbitrary general direction. Using the first Born approximation and the Dirac-Volkov states for charged particles, we derive an analytic expression for the decay rate. The direction of the laser field was found to have no significant effect on the nature of the result obtained. This study generalizes the results found for a field with a wave vector along the $z$-axis in a recent paper (Phys Rev D 102:073006, 2020). This paper will serve as a justification for the choice of a specific direction for the laser field in laser-assisted decay processes. The effect of the laser field on the total decay rate has also been reported and discussed.