The diagonal spin basis and calculation of processes involving polarized particles

Abstract

The review of developed by the authors new techniques for covariant calculation of matrix elements in QED, the so-called formalism of "Diagonal Spin Basis" (DSB), is presented. In DSB spin 4-vectors of in- and out- fermions are expressed just in terms of their 4-momenta. In this approach the little Lorentz group, common for the initial and final states,is realized. This brings the spin operators of in- and out-particles to coincidence. The developed approach is valid both for massive fermions and for massless ones. There occur no problems with accounting for spin flip amplitudes in it. Just 4-momenta of particles participating in reactions are required in it to construct the mathematical apparatus for calculations of matrix elements. We apply this formalism to the next processes: 1) Möller and Bhabha bremsstrahlung ($e^{\pm }{e}^{-}\to e^{\pm }{e}^{-}\gamma$) in the ultrarelativistic limit when initial particles and photon are helicity polarized; 2) Compton back-scattering of photons of intensive circularly polarized laser wave on a beam of longitudinally polarized ultrarelativistic electrons ($e+n{\gamma }_0\to e+\gamma$); 3) $e^{+}{e}^{-}$-pair production by a hard photon in simultaneous collision with several laser beam photons ($\gamma +n{\gamma }_0\to e^{+}+e^{-}$); 4) Bethe-Heitler process in the case of a linearly polarized photon emission by an electron with account for proton recoil and form factors; 5) the reaction $ep\to ep\gamma$ with proton polarizability being taken into account in the kinematics when proton bremsstrahlung dominates; 6) orthopositronium 3-photon annihilation ($e^{+}{e}^{-}\to 3\gamma$).

review, 50 pages, 6 figures

Cited by in corpus (7)

• Pair Creation in QED-Strong Pulsed Laser Fields Interacting with Electron Beams
• Emission and its back-reaction accompanying electron motion in relativistically strong and QED-strong pulsed laser fields
• New explicit expressions for Dirac bilinears
• Alternative way to understand the unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio
• On the physical meaning of Sachs form factors and on the violation of the dipole dependence of G_E and G_M on Q^2
• On the Measurement of Sachs Form Factors in Processes without and with Proton Spin Flip
• Generalized Sachs Form Factors and the Possibility of Their Measurement in Processes without and with Proton Spin Flip