Searcharxiv⌕ Search

arXiv subjects

Dmitry Borisyuk

Publications and source records attributed to Dmitry Borisyuk.

At least 19 recordsLinked to original sources
arXiv2020

Reanalysis of low-energy electron-proton scattering data and proton radius

We reanalyze electron-proton scattering data in the momentum transfer region $Q^2 < 1\ GeV^2$, which were used to determine proton electric radius, with main focus on the Mainz experiment (Bernauer et al., 2010). We examine dependence of fit results and $χ^2$ on the cut-off in $Q^2$ and degree of fitting polynomial, using pseudo-data and compare it with the case of real experimental data. We find that under some assumptions, the data could be consistent with the radius, obtained from muonic hydrogen.

hep-ph↗
arXiv2019

Two photon exchange in elastic electron scattering off hadronic systems

In the present review we discuss different aspects of the two-photon exchange (TPE) physics in elastic $ep$ scattering, at high $Q^2$ as well as at low $Q^2$. The imaginary part of the TPE amplitude gives rise to beam and target single-spin asymmetries. Different theoretical approaches to calculation of these observables are considered. The real part of the TPE amplitude influence unpolarized cross section and double-spin observables and is, most likely, responsible for discrepancy between two methods of proton form factors measurements. We review different methods of calculations of the TPE amplitudes the framework of "hadron" and "quark-gluon" approaches. We discuss the dispersion approach suitable for low and intermediate $Q^2$, which includes elastic and inelastic intermediate hadronic states, as well as connection of TPE to proton radius puzzle. The present situation with direct experimental searches for the TPE amplitude in $e^+p/e^-p$ charge asymmetry is also discussed, as well as attempts to extract the TPE amplitudes from existing experimental data obtained by the Rosenbluth and double polarization techniques. The TPE physics in other processes, such as elastic $μp$, $e$-nucleus and $eπ$ scattering is also reviewed.

hep-ph↗
arXiv2018

Two-photon exchange in nonrelativistic approximation

We calculate two-photon exchange amplitudes for the elastic electron-hadron scattering in the nonrelativistic approximation, and obtain analytical formulae for them. Numerical calculations are performed for proton and $^3$He targets. Comparing our numerical results with relativistic calculations, we find that the real part of the amplitude is described well at moderate $Q^2$, but the imaginary part strongly differs from the relativistic result. Thus the nonrelativistic approximation should not be used for calculation of observables which depend on the imaginary part of the amplitude, such as single-spin asymmetries.

hep-ph↗
arXiv2017

Meson exchange in lepton-nucleon scattering and proton radius puzzle

We study two-photon contribution to the elastic lepton-proton scattering, associated with sigma meson exchange, with special attention paid to the low-Q2 region. We show that the corresponding amplitude grows sharply but remains finite at Q2->0. The analytical formula for the amplitude at Q2=0 is obtained. We also estimate the shift of the muonic hydrogen energy levels, induced by sigma meson exchange. For the 2S level the shift is approximately 30 times smaller than needed to resolve the proton radius puzzle, but still exceeds the precision of the muonic hydrogen measurements.

hep-ph↗
arXiv2015

Two photon exchange amplitude with πN intermediate states: spin-1/2 and spin-3/2 channels

We calculate two-photon exchange (TPE) amplitudes for the elastic electron-proton scattering, and take into account intermediate hadronic states containing πN system with total angular momentum 1/2 or 3/2, which includes 8 different channels. This is the improvement of our previous calculation, where only the πN states with quantum numbers of Δ(1232) resonance were included. The results show good consistency with recent experimental data. At high Q^2, newly-calculated contributions affect the correction to the measured proton form factor ratio μG_E/G_M. The total correction becomes somewhat smaller compared to our previous work, but is still significant and grows approximately linearly with Q^2. Comparing contributions of different channels, we found that larger contributions come from the channels with quantum numbers of lightest resonances.

hep-ph↗
arXiv2015

TPEcalc: a program for calculation of two-photon exchange amplitudes

TPEcalc is a C++ program for calculation of two-photon exchange (TPE) amplitudes in elastic electron-hadron scattering, based on the dispersion method. It is a command-line tool which accepts kinematical parameters (Q^2 and epsilon) as input and returns TPE amplitudes. It can do calculations for proton, neutron and pion targets. Any spin 1/2+ or spin 0- target is supported, if the user supplies all necessary form factor parameterizations. This paper describes how to use TPEcalc and outlines underlying theory. The program source code can be downloaded from http://tpe.bitp.kiev.ua/

hep-ph↗
arXiv2014

On radiative corrections to polarization observables in electron-proton scattering

We consider radiative corrections to polarization observables in elastic electron-proton scattering, in particular, for the polarization transfer measurements of the proton form factor ratio $μG_E/G_M$. The corrections are of two types: two-photon exchange (TPE) and bremsstrahlung (BS); in the present work we pay special attention to the latter. Assuming small missing energy or missing mass cut-off, the correction can be represented in a model-independent form, with both electron and proton radiation taken into account. Numerical calculations show that the contribution of the proton radiation is not negligible. Overall, at high $Q^2$ and energies the total correction to $μG_E/G_M$ grows, but is dominated by TPE. At low energies both TPE and BS may be significant; the latter amounts to ~ 0.01 for some reasonable cut-off choices.

hep-ph↗
arXiv2014

Two photon exchange amplitude with πN intermediate states: P33 channel

We consider two-photon exchange (TPE) in the elastic electron-proton scattering and evaluate the effect of πN (pion + nucleon) intermediate hadronic states. Among different πN states, we concentrate on the P33 channel; thus we effectively include Delta(1232) resonance with realistic width and shape and corresponding background as well. In agreement with the previous result, obtained for the zero-width resonance, we observe that the TPE correction to the electric form factor is the largest one; it grows with Q^2 and at Q^2 > 2.5 GeV^2 exceeds the corresponding elastic contribution.

hep-ph↗
arXiv2012

On Delta resonance contribution to two-photon exchange amplitude

We consider two-photon exchange (TPE) in the elastic electron-proton scattering and study the contribution arising from the production of Delta(1232) resonance in the intermediate state. We calculate all three TPE amplitudes (generalized form factors), and find that the Delta contribution mainly influences generalized electric form factor (contrary to the elastic contribution, which affects magnetic form factor), and the effect grows with Q^2. If the corresponding correction is applied to the recent polarization transfer measurements of proton form factors, their results will change markedly. Thus we suggest that TPE corrections due to inelastic intermediate states are important to polarization experiments at high Q^2, and should not be neglected.

hep-ph↗
arXiv2011

Two-photon exchange in elastic electron-pion scattering

We calculate two-photon exchange amplitude for the elastic electron-pion scattering in the dispersion-relation inspired approach, including both elastic and inelastic contributions. The latter was modelled as a sum of ρand b_1(1235) meson contributions. We find that at Q^2 < 2 GeV^2 the elastic contribution is dominant, similarly to electron-proton scattering case. At higher Q^2 the inelastic contribution is not negligible, but still smaller than the elastic one. We also explain observed rapid amplitude growth at backward angles.

hep-ph↗
arXiv2010

Two-photon exchange amplitudes for the elastic $ep$ scattering at Q^2=2.5 GeV^2 from the experimental data

We extract two-photon exchange amplitudes for the elastic electron-proton scattering at Q^2=2.5 GeV^2 from the unpolarized cross-section and recent polarization transfer measurements. There are three independent amplitudes, but only one of them, δG_M, can be determined with a reasonable accuracy(about 10%). The result is in good agreement with theoretical predictions. Rough estimates for two other amplitudes are obtained.

hep-ph↗
arXiv2010

Proton charge and magnetic rms radii from the elastic $ep$ scattering data

The elastic electron-proton scattering data are analysed in order to determine proton charge and magnetic rms radii, r_E and r_M. Along with the usual statistical error, we try to estimate a systematic error in the radii, caused by the inadequacy of particular form factor parameterization employed. The range of data to use in the analysis is chosen so as to minimize the total (statistical + systematic) error. We obtain r_E = 0.912 +- 0.009 (stat) +- 0.007 (syst) fm, and r_M = 0.876 +- 0.010 (stat) +- 0.016 (syst) fm. The cross-section data were corrected for two-photon exchange. We found that without such corrections obtained r_E and r_M are somewhat smaller while the quality of fit is worse.

hep-ph↗
arXiv2008

Perturbative QCD predictions for two-photon exchange

We study two-photon exchange (TPE) in the elastic electron-nucleon scattering at high Q^2 in the framework of pQCD. The obtained TPE amplitude is of order alpha/alpha_s with respect to Born approximation. Its shape and value are sensitive to the choice of nucleon wavefunction, thus study of TPE effects can provide important information about nucleon structure. With the wavefunctions based on QCD sum rules, TPE correction to the electron-proton cross section has negative sign, is almost linear in epsilon and grows logarithmically with Q^2 up to 7% at Q^2 = 30 GeV^2. The results of existing "hadronic" calculations, taking into account just the nucleon intermediate state, can be smoothly connected with pQCD result near Q^2 = 3 GeV^2. Above this point two methods disagree, which implies that "hadronic" approach becomes inadequate at high Q^2. Other relevant observables, such as electron/positron cross section ratio, are also discussed.

hep-ph↗
arXiv2008

Two-photon exchange in dispersion approach

We calculate two-photon exchange amplitude for the elastic electron-proton scattering in the framework of dispersion relations. The imaginary part of the amplitude is determined by unitarity. Since in the unitarity relation intermediate states are on shell, off-shell form factors are not needed for the calculation. The real part is then evaluated using analytical properties of the amplitude. The expression for the elastic contribution to the amplitude, obtained in our approach, differs from the results of traditional calculations with on-shell form factors. Nevertheless, numerically the difference is minor for Q^2 up to 6 GeV^2.

nucl-th↗
arXiv2007

Electro-Magnetic Waves within a Model for Charged Solitons

We analyze the model of topological fermions (MTF), where charged fermions are treated as soliton solutions of the field equations. In the region far from the sources we find plane waves solutions with the properties of electro-magnetic waves.

hep-th↗
arXiv2007

Phenomenological analysis of two-photon exchange effects in proton form factor measurements

We perform a model-independent phenomenological analysis of experimental data on proton form factors ratio. We find that only one of the two photon exchange amplitudes, which we call $δG_M$, is responsible for the discrepancy between Rosenbluth and polarization methods. The linearity of Rosenbluth plots implies that $δG_M$ is approximately linear function of $ε$. The slope of $δG_M$ is extracted from experimental data and is shown to be consistent with theoretical calculations.

hep-ph↗
arXiv2006

Two-photon exchange at low Q^2

We study two-photon exchange for elastic electron-proton scattering at low Q^2. Compact approximate formulae for the amplitudes are obtained. Numerical calculations are done for Q^2 < 0.1 GeV^2 with several realistic form factor parameterizations, yielding similar results. They indicate that the corrections to magnetic form factor can visibly affect cross-section and proton radii. For low-Q^2 electron-neutron scattering two-photon exchange corrections are shown to be negligibly small.

nucl-th↗