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Quantum Electrodynamics Involving a Strong Laser Field

  When the laser field is strong, the simple formulas of Compton/Breit-Wheeler can nolonger be used. The laser strength is characterized by the parameter
where tex2html_wrap_inline10188 is the laser wavelength tex2html_wrap_inline10190 in meter, m the electron rest mass in eV/tex2html_wrap_inline7238, c the velocity of light in m/s, tex2html_wrap_inline10198, and P the power density in Watt/mtex2html_wrap_inline7792. When tex2html_wrap_inline10204, the simple formas are enough but as tex2html_wrap_inline7924 becomes large, the probability of absorbing more than one photon in the laser field cannot be ignored. When tex2html_wrap_inline10208, the constant-field approximationgif becomes good. If tex2html_wrap_inline10210, the expansion in terms of the number of absorbed photons, n, shows good convergence. The expansion takes a relatively simple form when the laser is circularly polarized by 100%. The present version accepts such case only.

In the case of the nonlinear Compton process  tex2html_wrap_inline10214, the number of emitted photons per unit time can be expanded in the formgif

    E, tex2html_wrap_inline10028
    Energy of the initial electron and final photon.
    tex2html_wrap_inline10220, tex2html_wrap_inline10222
    Helicity of the initial electron and laser (tex2html_wrap_inline10224, tex2html_wrap_inline10226).
    `Detector helicity' of the final electron and photon.
    Maximum photon energy when n laser photons are absorbed:
    Laser energy parameter: tex2html_wrap_inline10238. (tex2html_wrap_inline10240: laser photon energy)
    Functions involving Bessel functions. See Sec.A.1 for the definition.
The photon emission angle is uniquely determined from n and tex2html_wrap_inline10028.

The formula for the nonlinear Breit-Wheeler process  tex2html_wrap_inline10248 can be written in a similar form. The total number of pair electrons per unit time summed over the positron polarization is

    tex2html_wrap_inline10028, E
    Energy of the initial photon and final electron.
    tex2html_wrap_inline10254, tex2html_wrap_inline10256
    Initial photon helicity and `detector helicity' of the final electron.
    Laser energy parameter: tex2html_wrap_inline10260 (tex2html_wrap_inline10240: laser photon energy).
    Minimum energy of the final electron for given n:
    Functions involving Bessel functions. See Sec.A.2 for the definition.

When NPHtex2html_wrap_inline7900 is specified in LASERQED command, the above formulas are used with the terms upto n=NPH. See Sec.A for the algorithm of the event generation.

next up previous contents index
Next: Beamstrahlung Up: Laser Previous: Linear Compton Scattering

Toshiaki Tauchi
Thu Dec 3 17:27:26 JST 1998