Nonlinear effects in Compton scattering at photon colliders

Abstract

The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e→ γ conversion the density of laser photons in the conversion region should be so high that simultaneous interaction of one electron with several laser photons is possible (nonlinear Compton effect). In this paper a detailed consideration of energy spectra, helicities of final photons and electrons in nonlinear backward Compton scattering of circularly polarized laser photons is given. Distributions of γγ luminosities with total helicities 0 and 2 are investigated. Very high intensity of laser wave leads to broadening of the energy (luminosity) spectra and shift to lower energies (invariant masses). Beside complicated exact formulae, approximate formulae for energy spectrum and polarization of backscattered photons are given for relatively small nonlinear parameter ξ 2 (first order correction). All this is necessary for optimization of the conversion region at photon colliders and study of physics processes where a sharp edge of the luminosity spectrum and monochromaticity of collisions are important.

Complete description of polarization effects in emission of a photon by an electron in the field of a strong laser wave

“…Such a process with absorption of n = 1, 2, 3, 4 linearly polarized laser photons was observed in the recent experiment a d-ivanov@math.nsc.ru b kotkin@math.nsc.ru c serbo@math.nsc.ru at SLAC [6]. The polarization properties of the process (2) are important for a number of problems, for example, for laser beam cooling [7] and, especially, for future γγ and γe colliders (see [8,9] and the literature therein) . In the latter case the non-linear Compton scattering must be taken into account in simulations of the processes in the conversion region.…”

Loops and polarization in strong-field QED

“…The probability of nonlinear Compton scattering by an electron or a positron, or nonlinear Breit-Wheeler pair production, can now be expressed as (cf. [62][63][64][65][66][67])…”

Spectral characteristics of Compton backscattering sources. Linear and nonlinear modes

“…Note that the parameter n 2 ¼ a 2 0 =2 is also used in the literature [15]. The CBS cross section is most simply expressed through the invariant variables [16]:…”