The e+e− pair production by a probe photon traversing a linearly polarized laser pulse is treated as generalized nonlinear Breit-Wheeler process. For short laser pulses with very few oscillations of the electromagnetic field we find below the perturbative weak-field threshold s=2m a similar enhancement of the pair production rate as for circular polarization. The strong subthreshold enhancement is traced back to the finite bandwidth of the laser pulse. A folding model is developed which accounts for the interplay of the frequency spectrum and the intensity distribution in the course of the pulse.
@article{arxiv.1206.0159,
title = {Subthreshold pair production in short laser pulses},
author = {T. Nousch and D. Seipt and B. Kampfer and A. I. Titov},
journal= {arXiv preprint arXiv:1206.0159},
year = {2012}
}