Nonlinear effects in Compton scattering at photon colliders

The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e->gamma 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 gamma-gamma 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 xi^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.Comment: 21 pages, Latex, 6 figures(.ps), Talk at International Workshop on High Energy Photon Colliders; June 14-17, 2000, DESY, Hamburg, Germany; to be published in Nucl. Instr. and Methods

The lowest order inelastic QED processes at polarized photon-electron high energy collisions

The compact expressions for cross sections of photoproduction of a pair of charged particles $\mathrm{e}^+,\mathrm{e}^-$; $\mu^+,\mu^-$; $\pi^+,\pi^-$ as well as the double Compton scattering process are given. The explicit analytic expressions for the case of polarized photon and the initial electron in the kinematics when all the particles can be considered as a massless ones are presented. The photon polarization is described in the terms of Stokes parameters.Comment: LaTeX2e, 9 page

Angular Dependence of the Polarization Transfer to the Proton in the ep⃗→ep⃗e \vec p \to e \vec p Process

The dependence of the longitudinal polarization transfer to the proton in the $e \vec p \to e \vec p$ process on the proton scattering angle has been numerically analyzed for the case where the initial (at rest) proton is partially polarized along the direction of motion of the detected recoil proton. The analysis is based on the results of JLab polarization experiments on measuring the ratio of the Sachs form factors in the $\vec e p \to e \vec p$ process using the Kelly (2004) and Qattan (2015) parameterizations for their ratio, in the kinematics of the SANE Collaboration experiment (2020) on measuring the double spin asymmetry in the $\vec e \vec p \to e p$ process. It is shown that the violation of the scaling of the Sachs form factors leads to a significant increase in the magnitude of the polarization transfer to the proton in comparison with the case of dipole dependence.Comment: 7 pages, 4 figures, 2 tables; version published in the JETP Letter

New Method for Measuring the Ratio μpGE/GM\mu_p G_E/G_M Based on the Polarization Transfer from the Initial Proton to the Final Electron in the ep⃗→e⃗pe \vec p \to \vec e p Process

In this letter, we propose a new method for measuring the Sachs form factors ratio ($R =\mu_p G_E/G_M$) based on the transfer of polarization from the initial proton to the final electron in the elastic $e \vec p \to \vec e p$ process, in the case when the axes of quantization of spins of the target proton at rest and of the scattered electron are parallel, i.e., when an electron is scattered in the direction of the spin quantization axis of the proton target. To do this, in the kinematics of the SANE collaboration experiment (2020) on measuring double spin asymmetry in the $\vec e\vec p \to e p$ process, using Kelly (2004) and Qattan (2015) parametrizations, a numerical analysis was carried out of the dependence of the longitudinal polarization degree of the scattered electron on the square of the momentum transferred to the proton, as well as on the scattering angles of the electron and proton. It is established that the difference in the longitudinal polarization degree of the final electron in the case of conservation and violation of scaling of the Sachs form factors can reach 70%. This fact can be used to set up polarization experiments of a new type to measure the ratio $R$.Comment: 6 pages, 4 figures, 2 tables, for greater clarity, some minor additions have been mad

QED peripheral mechanism of pair production at colliders

Cross section of the processes of neutral pion production as well as pairs of charged fermions and bosons in peripherical interaction of leptons, photons are calculated in main logarithmical approximation. We investigate the phase volumes and differential cross sections. The differential cross section of few neutral pions and a few pairs production are written down explicitly. Considering the academic problem of summation on the number of pairs for the case of massless particles we reproduce the known results obtained in seventies of last century. The possibility to construct the generator for Monte-Carlo modeling of this processes basing of this results are discussed.Comment: 25 pages, 5 figure

Polarized triplet production by circularly polarized photons

A process of the pair production by a circularly polarized photon in the field of unpolarized atomic electron has been considered in the Weizaecker-Williams approximation. The degree of longitudinal polarization of positron and electron has been calculated. An exclusive cross-section as well as a spectral distribution are obtained. We estimate the accuracy of our calculations at the level of a few percent. We show the identity of the positron polarization for considered process and for process of pair production in the screened Coulomb field of nucleus.Comment: 9 pages, 3 picture