arXiv subjects

M. V. Galynskii

Publications and source records attributed to M. V. Galynskii.

17 recordsLinked to original sources

arXiv2024

Polarization effects in the elastic $e \vec p \to \vec e p$ and $\vec e \vec p \to e p$ processes in the case of parallel spins

In the one-photon exchange approximation, we analyze polarization effects in the elastic $\vec e \vec p \to e p$ and $ e \vec p \to \vec e p$ processes in the case when the spin quantization axes of a target proton at rest and an incident or scattered electron are parallel. To do this, in the kinematics of the SANE Collaboration experiment, using the J. Kelly and I. Qattan parametrizations for the Sachs form factor ratio $R\equiv μ_p G_E/G_M$, a numerical analysis was carried out of the dependence of the longitudinal polarization degree transferred to the scattered electron in the $e \vec p \to \vec e p$ process and double spin asymmetry in the $\vec e \vec p \to e p$ process on the square of the momentum transferred to the proton as well as on the scattering angle of the electron. It is established that the difference in the longitudinal polarization degree of the scattered electron in the $ e \vec p \to \vec e p$ process in the case of conservation and violation of the 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 $R$. For double spin asymmetry in the $\vec e \vec p \to e p$ process, the corresponding difference does not exceed 2.32 \%. This fact means that it's not sensitive to the effects of the Sachs form factor scaling violation and could be used as test for the $R\approx 1$ equality.

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arXiv2023

New Method for Measuring the Ratio $μ_p G_E/G_M$ Based on the Polarization Transfer from the Initial Proton to the Final Electron in the $e \vec p \to \vec e p$ Process

In this letter, we propose a new method for measuring the Sachs form factors ratio ($R =μ_p G_E/G_M$) 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 $R$.

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arXiv2022

Angular Dependence of the Polarization Transfer to the Proton in the $e \vec p \to e \vec p$ 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.

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arXiv2022

Reliability Analysis of the Results of the Known Experiments on Measuring of the Sachs Form Factor Ratio Using the Rosenbluth Technique. Polarization of the Final Proton in the $e \vec p \to e \vec p$ Elastic Process

A criterion for assessing the reliability of measurements of the Sachs form factor ratio using the Rosenbluth technique is proposed and applied to an analysis of three known experiments (Andivahis1994, Walker1994, Qattan2005) and a recent experiment on the CEBAF accelerator upgraded to 12 GeV at JLab (arXiv:2103.01842 [nucl-ex]). Based on the results of the JLab polarization experiments on measuring the ratio $μ_p G_E/G_M$ in the $\vec e p \to e \vec p$ process, in the kinematics of the SANE Collaboration experiment (2020) on the measurement of double spin asymmetry in the $\vec e \vec p \to e p$ process numerical calculations are performed for the $Q^2$ dependence of polarization transferred to the proton in the $e \vec p \to e \vec p$ process when the initial proton at rest is partially polarized along the direction of motion of the detected recoil proton.

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arXiv2021

On the Transfer of Polarization from the Initial to the Final Proton in the Elastic Process $ e \vec {p} \to e \vec {p}$

The $Q^2$ dependence of the ratio of the cross sections with and without proton spin flip, as well as the polarization asymmetry in the process $e \vec{p} \to e \vec{p}$ has been numerically analyzed using the results of JLab polarization experiments on the measurements of the ratio of the Sachs form factors in the $\vec{e} p \to e \vec{p}$ process. The calculations have been made for the case where the initial (at rest) and final protons are fully polarized and have a common spin quantization axis, which coincides with the direction of motion of the final proton. The longitudinal polarization transfer to the proton has been calculated in the case of the partially polarized initial proton for a kinematics used in the experiment reported in [A. Liyanage et al. (SANE Collaboration), Phys. Rev. C 101, 035206 (2020)], where the double spin asymmetry was measured in the $\vec{e} \vec{p} \to e p$ process. A noticeable sensitivity of the polarization transfer to the proton to the form of the $Q^2$ dependence of the ratio $μ_p G_E/G_M$ has been found. This sensitivity may be used to conduct a new independent experiment to measure this dependence in the $ e \vec{p} \to e \vec{p}$ process. A criterion to assess the reliability of measurements of the ratio of Sachs form factors using the Rosenbluth technique has been proposed and used to analyze the results of two experiments.

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arXiv2020

Generalized Sachs Form Factors and the Possibility of Their Measurement in Processes without and with Proton Spin Flip

The differential cross section for elastic electron proton scattering has been calculated taking into account the two photon exchange within the phenomenological description of the electromagnetic electron proton interactions. The calculation is based on the consistent evaluation of the matrix elements of the proton current in a diagonal spin basis, which makes it possible to naturally obtain expressions for the generalized Sachs form factors. A new method has been proposed to independently measure these form factors in the elastic $e \vec{p} \to e \vec{p}$ process in the case where the initial proton at rest is fully polarized along the direction of the motion of the final proton.

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arXiv2019

On the Measurement of Sachs Form Factors in Processes without and with Proton Spin Flip

The physical meaning of the decomposition of the Rosenbluth formula into two terms containing only squares of Sachs form factors has been established. A new method has been proposed for their independent measurement in the $e \vec{p} \to e \vec{p}$ elastic process when the initial proton at rest is fully polarized along the direction of motion of the final proton.

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arXiv2014

Alternative way to understand the unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio

In the one-photon exchange approximation we discuss questions related to the interpretation of unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio $G_E/G_M$ in the region $1. 0 \leq Q^2 \leq 8.5$ GeV$^2$. For this purpose, we developed an approach which essentially is a generalization of the constituent-counting rules of the perturbative QCD (pQCD) for the case of massive quarks. We assume that at the lower boundary of the considered region the hard-scattering mechanism of pQCD is realized. Within the framework of the developed approach we calculated the hard kernel of the proton current matrix elements $J^{\pm δ, δ}_{p}$ for the full set of spin combinations corresponding to the number of the spin-flipped quarks, which contribute to the proton transition without spin-flip ($J^{δ, δ}_{p}$) and with the spin-flip ($J^{-δ, δ}_{p}$). This allows us to state that (i) around the lower boundary of the considered region, the leading scaling behavior of the Sachs form factors has the form $G_E, G_M \sim 1/Q^6$, (ii) the dipole dependence ($G_E, G_M \sim 1/Q^4$) is realized in the asymptotic regime of pQCD when $τ\gg 1$ ($τ=Q^2/4M^2$) in the case when the quark transitions with spin-flip dominate, (iii) the asymptotic regime of pQCD in the JLab experiments has not yet been achieved, and (iv) the linear decrease of the ratio $G_{E}/G_{M}$ at $τ< 1$ is due to additional contributions to $J^{δ, δ}_{p}$ by spin-flip transitions of two quarks and an additional contribution to $J^{-δ, δ}_{p}$ by spin-flip transitions of three quarks.

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arXiv2013

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

We discuss questions related to the interpretation of unexpected results of measurements of the proton form factors ratio G_E/G_M in the polarization experiments done in JLab in the region of 0.5 < Q^2 < 8.5 GeV^2. For this purpose, in the case of the hard scattering mechanism we calculated (in the leading approximation) the matrix elements of the proton current J^{\pm δ,δ}_p for the full set of spin combinations corresponding to the number of the spin-flipped quarks, which contribute to the proton transition without spin-flip (J^{δ,δ}_p) and with the spin-flip (J^{-δ,δ}_p). This set is: (0,1), (0,3), (2,1), (2,3), where the first number in parentheses is the number of the spin-flipped quarks, which contribute to the J^{δ,δ}_p, and the second one is the number of the spin-flipped quarks which contribute to the J^{-δ,δ}_p. For the sets of (0,1) and (2,3), we found that the ratio G_E/G_M ~ 1, and the form factors G_E and G_M behave for the set of (0,1) as G_E, G_M ~ 1/Q^6, and for the set of (2,3) as G_E, G_M ~ 1/Q^4. At the same time the set of (0,1) is realized for τ<< 1, and the set (2,3) for τ>> 1 (τ=Q^2/4m^2). This allows us to suppose that: 1) at the lower boundary of the experimental measurements of the ratio G_E/G_M not dipole dependence appears but the law of G_E, G_M ~ 1/Q^6; 2) the conditions for the observation of the dipole dependence in the experiments has not yet been achieved; 3) since for quarks J^{δ,δ}_q ~ 1 and J^{-δ,δ}_q ~ \sqrtτ, then the dipole dependence is realized when τ>> 1 in the case when the quark transitions with spin-flip are dominate.

nucl-th↗

arXiv2008

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 $ep \to ep γ$ and $γp \to e \bar e p$ 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.

hep-ph↗

arXiv2008

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.

hep-ph↗

arXiv2007

QED processes in peripheral kinematics at polarized photon-photon and photon-electron colliders

The calibration QED process cross sections for experiments on planned electron-photon and photon-photon colliders for detecting the small angles scattered particles are calculated. These processes describe the creation of two jets moving sufficiently close to the beam axis directions. The jets containing two and three particles including charged leptons, photons and pseudoscalar mesons are considered explicitly. Considering the pair production subprocesses we take into account both bremsstrahlung and double photon mechanisms. The obtained results are suitable for further numerical calculations.

hep-ph↗

arXiv2006

Radiative corrections to chiral amplitudes in quasiperipheral kinematics

Chiral amplitudes for two jets processes in quasi-peripheral kinematics are calculated at the Born and one loop correction level. The amplitudes of subprocesses describing interaction of virtual and real photon with creation of a charged fermion pair for various chiral states are considered in details. Similar results are presented for Compton subprocess with virtual photon. Contribution of emission of virtual, soft, and hard real additional photons are taken into account explicitly. The relevant cross sections expressed in terms of impact factors are in agreement with structure function approach in the leading logarithmical approximation. Contributions of the next to leading terms are presented in an analytical form. Accuracy estimation is discussed.

hep-ph↗

arXiv2003

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 $\mathrm{e}^+,\mathrm{e}^-$; $μ^+,μ^-$; $π^+,π^-$ 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.

hep-ph↗

arXiv2003

Calibration processes for photon-photon colliders

Processes with creation of a pair charged particles with emission of hard photon and two pairs of charged particles are considered for colliding partially polarized photon photon beams. The effects of circular and linear polarization of the initial photons are discussed in more details.

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arXiv2002

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.

hep-ph↗

arXiv1999

The diagonal spin basis and calculation of processes involving polarized particles

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 ($e^{\pm}e^- \to e^{\pm}e^- γ$) 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 ($e+nγ_0 \to e+γ$); 3) $e^+e^-$-pair production by a hard photon in simultaneous collision with several laser beam photons ($γ+n γ_0 \to e^+ + e^-$); 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 $ep \to ep γ$ with proton polarizability being taken into account in the kinematics when proton bremsstrahlung dominates; 6) orthopositronium 3-photon annihilation ($e^+e^{-} \to 3 γ$).

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