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

Possible Method for Measuring the Proton Form Factors in Processes with and without Proton Spin Flip

The ratio of the squares of the electric and magnetic proton form factors is shown to be proportional to the ratio of the cross sections for the elastic scattering of an unpolarized electron on a partially polarized proton with and without proton spin flip. The initial proton at rest should be polarized along the direction of the motion of the final proton. Similar results are valid for both radiative $ep$ scattering and the photoproduction of pairs on a proton in the Bethe--Heitler kinematics. When the initial proton is fully polarized in the direction of the motion of the final proton, the cross section for the $ep \to ep$ process, as well as for the $ep \to ep \gamma$ and $\gamma p \to e \bar e p$ processes, without (with) proton spin flip is expressed only in terms of the square of the electric (magnetic) proton form factor. Such an experiment on the measurement of the cross sections without and with proton spin flip would make it possible to acquire new independent data on the behavior of $G_E^2(Q^2)$ and $G_M^2(Q^2)$, which are necessary for resolving the contradictions appearing after the experiment of the JLab collaboration on the measurement of the proton form factors with the method of polarization transfer from the initial electron to the final proton.Comment: 7 pages, revtex

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