General Seminars

Quantum processes in short and intensive electromagnetic pulses

by Dr. Alexandr Titov (Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna)

Wednesday, 27 May 2015 from to (Europe/Bucharest)
at Magurele ( National Library of Physics )
We discuss some  aspects of two widely discussed  quantum processes. The
first one is  the non-linear Breit -Wheeler process, i.e. the  emission of
$\ee$ pairs off a probe photon propagating through a polarized short-pulsed
electromagnetic (e.g.\ laser) wave field.  The second one is a photon
emission off an electron interacting with the laser pules (non-linear
Compton scattering). Our consideration is done within a QED framework.
 We show that the production probability is determined by the interplay of
two dynamical effects. The first one is related to the shape and duration of
the pulse and the  second one is the non-linear dynamics of the interaction
of charged fermions with the strong electromagnetic field.
 The first effect manifests itself most clearly in the weak-field regime,
where the small field intensity is compensated by the rapid variation of the
electromagnetic field in a limited  space-time region, which intensifies the
few-photon events and can enhance the production probability by orders of
magnitude compared to an infinitely long pulse.
In other words, the short pulses may be considered as a powerful amplifiers.
The non-linear dynamics in essentially multi-photon interactions  plays a
decisive role at large field intensities, where effects of the pulse shape
and duration are less important. In the transition regime, both effects must
be taken into account simultaneously. We provide suitable expressions for
the production  probabilities/cross sections for kinematic regions  which
can be used in transport codes.