We propose a new method to compute amplitudes of electroweak processes in the strong background magnetic field, using $\gamma\to e^+e^-$ as an example. We show that the { \it moments} of $\gamma\to e^+e^-$ width are proportional to the derivatives of photon polarization function at the zero energy. Hence, the pair-production width can be easily calculated from the latter by the inverse Mellin transform. The prospects of our approach are commented.
Categories: hep-ph