Triplet production by a polarized photon beam on a polarized electron target

Abstract

The cross section and polarization observables in the process of the electron-positron pair photoproduction on a free electron are calculated. The double differential distributions, over the square of the 4-momentum transfer to the recoil electron q2 , and the square of the created e+e− - invariant mass , Q2 are obtained in the target-electron rest frame taking into account the contributions of the socalled Borsellino and (γ − e) diagrams. The integration of these distributions over q2 (and over Q2 ) is performed and the results are analyzed mainly in those kinematical regions where the (γ - e)-contribution is larger (or the same order) than (as) the Borsellino one. Such calculations are motivated by the experiments in search of the possible dark matter candidate (light U-boson) in process of triplet photoproduction. The original analytical formulas for q2 (and Q2 ) distributions can be used to check the work of the corresponding Monte Carlo generators. We consider the following cases: particles are unpolarized, photon beam is linearly polarized, photon beam is circularly polarized at polarized electron target.