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E. Kuraev

Publications and source records attributed to E. Kuraev.

At least 19 recordsLinked to original sources
arXiv2014

Coulomb Corrections to the Parameters of the Landau-Pomeranchuk-Migdal Effect Theory and its Analogue

Using the Coulomb correction to the screening angular parameter of the Moliere multiple scattering theory, we obtained analytically and numerically the Coulomb corrections to the parameters of the Migdal LPM effect theory. We showed that these corrections allow to eliminate the discrepancy between the predictions of the LPM effect theory and its measurement at least for high Z targets and also to further improve the agreement between the predictions of the LPM effect theory analogue for a thin layer of matter and experimental data.

hep-ph↗
arXiv2013

NLO and NNLO EWC for PV Moller Scattering

High-precision electroweak experiments such as parity-violating Moller scattering can provide indirect access to physics at multi-TeV scales and play an important complementary role to the LHC research program. However, before physics of interest can be extracted from experimental data, electroweak radiative corrections, which can significantly reduce the cross-section asymmetry, must be calculated with an unprecedented completeness and accuracy. Although the two-loop corrections are strongly suppressed relative to the one-loop corrections, they can no longer be dismissed for the upcoming precision experiments. We evaluate a full gauge-invariant set of one-loop and several types of two-loop radiative corrections for the parity-violating electron-electron scattering asymmetry by combining two distinct but mutually-reinforcing techniques: semiautomatic, precise, with FeynArts and FormCalc as base languages, and by hand, with some approximations. For 11 GeV relevant for the ultra-precise MOLLER experiment planned at JLab, the results obtained by two approaches are in excellent agreement, which gives us assurance that our calculations are error-free.

hep-ph↗
arXiv2011

High precision calculations of electroweak radiative corrections for polarized Moller scattering at one loop and beyond

Parity-violating Moller scattering measurements are a powerful probe of new physics effects, and the upcoming high-precision experiments will require a new level of accuracy for electroweak radiative corrections (EWC). First, we perform the updated calculations of one-loop EWC for Moller scattering asymmetry using two different approaches: semi-automatic, precise, with FeynArts and FormCalc as base languages, and "by hand", with reasonable approximations. In addition, we provide a tuned comparison between the one-loop results obtained in two different renormalization schemes: on-shell and constrained differential renormalization. As the last step, we discuss the two-loop EWC induced by squaring one-loop diagrams, and show that the significant size of this partial correction indicates a need for a complete study of the two-loop EWC in order to meet the precision goals of future experiments.

hep-ph↗
arXiv2011

Quadratic electroweak corrections for polarized Moller scattering

The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity violating electron-electron scattering asymmetry induced by squaring one-loop diagrams. The calculations are relevant for the ultra-precise 11 GeV MOLLER experiment planned at Jefferson Laboratory and experiments at high-energy future electron colliders. The imaginary parts of the amplitudes are taken into consideration consistently in both the infrared-finite and divergent terms. The size of the obtained partial correction is significant, which indicates a need for a complete study of the two-loop electroweak radiative corrections in order to meet the precision goals of future experiments.

hep-ph↗
arXiv2009

Predictions for high-energy pp and \bar pp scattering from a finite sum of gluon ladders

An eikonalized elastic proton-proton and proton-antiproton scattering amplitude F(s,t), calculated from QCD as a finite sum of gluon ladders, is compared with the existing experimental data on the total cross section and the ratio ρ(s,0)=Re F(s,0)/Im F(s,0) of the real part to the imaginary part of the forward amplitude. Predictions for the expected LHC energies are given.

hep-ph↗
arXiv2007

Double logarithmical corrections to beam asymmetry in polarized electron-proton scattering

The up-down asymmetry in transversally polarized electron proton scattering is induced by the interference between one and two photon exchange amplitudes. Inelastic intermediate hadronic states (different from one-proton state) of the two photon exchange amplitude give rise to contributions containing the square of "large logarithm" (logarithm of the ratio of the transferred momentum to the electron mass). We investigate the presence of such contributions in higher orders of perturbation theory. The relation with the case of zero transfer momentum is explicitly given. The mechanism of cancellation of infrared singularities is discussed.

hep-ph↗
arXiv2006

Polarization transfer measurements of proton form factors: deformation by initial collinear photons

It is demonstrated that an emission of collinear photons by the polarized initial electron in elastic electron-proton polarization transfer scattering leads to an apparent shifting of real events with small momentum transfer into the data sample with large momentum transfer. Effectively this shows a fictive enhancement of the cross section at large momentum transfer. However, the enhancement is different for transverse and longitudinal polarizations of the recoil proton. The former is responsible for a deformation of results when extracting the proton electromagnetic form factors ratio from the data on electron-proton polarization transfer scattering. Nevertheless, this effect does not explain the suppression of the Dirac form factor at large momentum transfer completely.

hep-ph↗
arXiv2002

Two comments to utilization of structure function approach in DIS experiments

The "returning to resonance" mechanism can be used to obtain the simple procedure of taking RC to DIS cross section into account, in frames of Drell-Yan picture. Iteration procedure is proposed. Kinematic region $y \to 1$ can be described in frames of Drell-Yan picture using structure function approach. The large RC in the lowest order reflect Sudakov form factor suppression, which can be taken into account in all orders of perturbation theory. Basing on explicit calculation in two lowest orders of perturbation theory we construct the cross section in $y \to 1$ region obeying renormalization group equations and include the Sudakov-like form factor suppression.

hep-ph↗
arXiv2002

Radiative Corrections to the $K_{e3}^{\pm}$ Decay Revised

We consider the lowest order radiative corrections for the decay $K^{\pm}\to π^0 e^{\pm} ν$, usually referred as $K_{e3}^{\pm}$ decay. This decay is the best way to extract the value of the $V_{us}$ element of the CKM matrix. The radiative corrections become crucial if one wants a precise value of $V_{us}$. The existing calculations were performed in the late 60's \cite{B,G} and are in disagreement. The calculation in \cite{G} turns out to be ultraviolet cutoff sensitive. The necessity of precise knowledge of $V_{us}$ and the contradiction between the existing results constitute the motivation of our paper. We remove the ultraviolet cutoff dependence by using A.Sirlin's prescription; we set it equal to the $W$ mass. We establish the whole character of small lepton mass dependence based on the renormalization group approach. In this way we can provide a simple explanation of Kinoshita--Lee--Nauenberg cancellation of singularities in the lepton mass terms in the total width and pion spectrum. We give an explicit evaluation of the structure--dependent photon emission based on ChPT in the lowest order. We estimate the accuracy of our results to be at the level of 1%. The corrected total width is $Γ=Γ_0(1+δ)$ with $δ=0.02\pm0.0002$. Using the formfactor value $f_+(0)=0.9842\pm 0.0084$ calculated in \cite{CKNRT} leads to $|V_{us}|=0.2172 \pm0.0055$.

hep-ph↗
arXiv2002

Scalar and pseudoscalar meson pole terms in the hadronic light-by-light contributions to $a_μ^{had}$

Third QED order hadronic light-by-light (LBL) contributions $a_μ^{LBL}(M)$ to the anomalous magnetic moment of the muon $a_μ^{had}$ from the pole terms of scalar $σ$, $a_0(980)$ and pseudoscalar $π^0$, $η$, $η'$ mesons (M) in the framework of the linearized extended Nambu-Jona-Lasinio model are evaluated. The off-shell structure of the photon-photon-meson vertices is taken into account by means of constituent quark triangle loops. The mass of the quark is taken to be $m_u=m_d=m_q=(280 \pm 20)$ MeV. The unknown strong coupling constants of $π^0, η, η'$ and $a_0$ mesons with quarks are evaluated in a comparison of the corresponding theoretical two-photon widths calculated in the framework of our approach with experimental ones. The $σ$-meson coupling constant is taken to be equal to $π_0$-meson coupling constant as it follows from the linearized Nambu-Jona-Lasinio model Lagrangian. Then one obtains $a_μ^{LBL}(π_0)$=$(81.83 \pm 16.50) \times 10^{-11}$, $a_μ^{LBL}(η)$=$(5.62 \pm 1.25) \times 10^{-11}$, $a_μ^{LBL}(η')$=$(8.00 \pm 1.74) \times 10^{-11}$, $a_μ^{LBL}(σ)$=$(11.67 \pm 2.38) \times 10^{-11}$ and $a_μ^{LBL}(a_0)$=$(0.62 \pm 0.24) \times 10^{-11}$. The total contribution of meson poles in LBL is $a_μ^{LBL}(M)$=$(107.74 \pm 16.81) \times 10^{-11}$.

hep-ph↗
arXiv2001

Single-spin asymmetry in DVCS: fragmentation region of polarised lepton

For the kinematical region when a hard photon is emitted predominantly close to the direction of motion of a longitudinally polarized initial electron and relatively small momentum transfer to a proton we calculate the azimuthal asymmetry of photon emission. It arises from the interference of the Bethe-Heitler amplitude and those which are described by a heavy photon impact factor. Azimuthal asymmetry does not decrease in the limit of infinite cms energy. Lowest order expression for the impact factor of a heavy photon is presented.

hep-ph↗
arXiv2000

Nonlinear effects in Compton scattering at photon colliders

The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e->gamma conversion the density of laser photons in the conversion region should be so high that simultaneous interaction of one electron with several laser photons is possible (nonlinear Compton effect). In this paper a detailed consideration of energy spectra, helicities of final photons and electrons in nonlinear backward Compton scattering of circularly polarized laser photons is given. Distributions of gamma-gamma luminosities with total helicities 0 and 2 are investigated. Very high intensity of laser wave leads to broadening of the energy (luminosity) spectra and shift to lower energies (invariant masses). Beside complicated exact formulae, approximate formulae for energy spectrum and polarization of backscattered photons are given for relatively small nonlinear parameter xi^2 (first order correction). All this is necessary for optimization of the conversion region at photon colliders and study of physics processes where a sharp edge of the luminosity spectrum and monochromaticity of collisions are important.

hep-ph↗
arXiv2000

P-violating effects in low-energy Compton scattering

Parity of effects induced by one loop corrections of Standard model of Compton scattering are considered. We note the main effects arise from W contributions. Keeping in the mind scheme independent gauge invariance amplitude we calculated the one spin asymmetries for the case when initial electron is polarized and the case of circular polarized photon. They are of order $10^{-13}$.

hep-ph↗
arXiv2000

Charge-odd and single-spin effects in two-pion production in ep collisions

We consider double-photon and bremsstrahlung mechanisms for the production of two charged pions in high-energy electron (or proton) scattering off a transversely polarised proton. Interference between the relevant amplitudes generates a charge-odd contribution to the cross-section for the process. In the kinematical configuration with a jet nearly collinear to the electron, the spin-independent part may be used to the determine phase differences for pion-pion scattering in states with orbital momentum 0 or 2 and 1, while for the configuration with a jet nearly collinear to the proton, the spin-dependent part may be used to explain the experimental data for single-spin correlations in the production of negatively charged pions. We also discuss the backgrounds and estimate the accuracy of the results to be better than 10 %. In addition, simplified formulae derived for specific kinematics, with small total transverse pion momenta, are given. The accuracy is estimated to remain at the same level despite the lower energy.

hep-ph↗
arXiv2000

QED correction to radiative tail from elastic peak in DIS

We calculate DIS cross section under kinematical requirements when a final hadron state is a single proton. The process in the lowest order is known as radiative tail from elastic peak. We take into account correction, coming from emission of virtual and soft real photons, to the amplitude of this process as well as the one, induced by emission of additional hard photon and a hard pair. Resulting contributions of these channels are presented in the leading and, partly, next-to-leading logarithmic approximations. Some general expressions for the photon contributions are given. Numerical results are presented for kinematical conditions of the current experiments on DIS.

hep-ph↗
arXiv1999

Helicity amplitudes for the small--angle process e^-e^{\pm}\to e^-γγ+ e^{\pm} with both photons along one direction and its cross channel

We study the small--angle double bremsstrahlung in $e^-e^\pm$ scattering for a jet kinematics where both photons move along the electron direction. This region gives the main contribution to the cross section. We present analytic expressions for all 64 amplitudes with arbitrary helicity states of the initial and final leptons and the produced photons convenient for analytic and numerical studies. The accuracy of the obtained amplitudes is given omitting only terms of the order of m^2/E_j^2, θ_j^2 and θ_j m/E_j. The helicity amplitudes for the cross channel γe^\pm \to γe^+e^- + e^\pm are given. Several limits for the helicity amplitudes of hard or soft final particles are considered.

hep-ph↗