arXiv subjects

M. V. Bondarenco

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

At least 19 recordsLinked to original sources

arXiv2021

Nuclear and electronic contributions to Coulomb correction for Moliere screening angle

The Coulomb correction (difference from the 1st Born approximation) to the Molière screening angle in multiple Coulomb scattering theory is evaluated with the allowance for inelastic contribution. The controversy between dominance of close- or remote-collision contributions to Coulomb correction is discussed. For scattering centres represented by a Coulomb potential with a generic (not necessarily spherically symmetric) creening function, the Coulomb correction is proven to be screening-independent, by virtue of the eikonal phase cancellation in regions distant from the Coulomb singularity. Treating the atom %more self-consistently, as an assembly of pointlike electrons and the nucleus, and summing the scattering probability over all the final atom states, it is shown that besides the Coulomb correction due to close encounters of the incident charged particle with atomic nuclei, there are similar corrections due to close encounters with atomic electrons (an analog of Bloch correction). For low $Z\neq1$ the latter contribution can reach $\sim 25\%$, but its observation is partly obscured by multiple scattering effects.

physics.atom-ph↗

arXiv2021

Correlation between multiple scattering angle and ionization energy loss for fast electrons

A correlation between the angle of multiple scattering and the ionization energy loss for relativistic electrons in an amorphous medium is computed by solving the combined transport equation. The correlation is found to be the most pronounced at deflection angles larger than typical, reflecting the underlying single-scattering kinematical correlation, but is also sizable at typical deflection angles, where the width of the angular distribution increases with the increase of the energy loss. The mean energy loss as a function of the deflection angle is calculated. It grows quadratically both at small and at large angles, but the proportionality coefficient at large angles is greater than at small ones.

hep-ph↗

arXiv2020

Mean volume reflection angle

The mean volume reflection angle of a high-energy charged particle passing through a bent crystal is expressed as an integral involving the effective interplanar potential over a single crystal period. Implications for positively and negatively charged particles, and silicon crystal orientations (110) and (111) are discussed. A generic next-to-leading-order expansion in the ratio $E/R$ of the particle energy $E$ to the crystal bending radius $R$ is given. For positively charged particles, the dependence of the mean volume reflection angle on $E/R$ proves to be approximately linear, whereas for negatively charged particles the linear behaviour is modified by an $E/R$-dependent logarithmic factor. Up-to-date experimental data are confronted with predictions based on commonly used atomic potentials.

physics.acc-ph↗

arXiv2018

Tips for Deciphering and Quick Calculation of Radiation Spectra

Radiation spectra from ultra-relativistic electrons in thin [$T\ll l_f(ω)$] and thick [$T\gg l_f(ω)$] targets are discussed. The method of simplified averaging is described by examples of Landau-Pomeranchuk-Migdal effect and radiation at doughnut scattering. General infrared and ultraviolet asymptotic properties of radiation spectra are discussed.

hep-ph↗

arXiv2018

Separation Of Edge Effects In Highly Non-Dipole Radiation Spectra

Edge effects in spectra of non-dipole radiation from ultra-relativistic electrons passing through various finite targets are analyzed from a unified point of view. Examples include radiation in a finite magnet, bremsstrahlung at double scattering, and bremsstrahlung in an amorphous plate. A generalization of the encountered spectral decomposition property is proposed. The relevance of phenomena of jet-interjet radiation interference and electron time delay in the target is emphasized. Features produced by them in the radiation spectra are discussed.

hep-ph↗

arXiv2017

Next-to-leading order correction to the factorization limit of the radiation spectrum

A next-to-leading order correction to the high-energy factorization limit of radiation spectrum from an ultrarelativistic electron scattering in an external field is evaluated. Generally, it does not express through scattering characteristics, and accounts for smoothness of the crossover between the initial and final electron asymptotes. A few examples of application of this formula are given, including bremsstrahlung in amorphous matter and undulator radiation.

hep-ph↗

arXiv2017

Interference in spectrum of radiation from doubly scattered charged particle

Existence of different types of interference in the spectrum of radiation emitted by a doubly hard scattered electron is demonstrated. The spectrum develops oscillations in two regions: the hard, where the oscillations depend on the electron Lorentz factor, and the soft, where the oscillations depend on the electron scattering angles. This interference pattern owes to the presence of jetlike radiation configurations, formed by a piecewise-rectilinearly moving electron and the accompanying photon. The corresponding nondipole decomposition relation is derived. Notions describing proper field formation and interference, and presumably being applicable more generally, are discussed in detail.

physics.acc-ph↗

arXiv2016

Improved separation of soft and hard components in multiple Coulomb scattering

Evaluation of the angular distribution function of particles scattered in an amorphous medium is improved by deforming the integration path in the Fourier integral representation into the complex plane. That allows us to present the distribution function as a sum of two positive components, soft and hard, the soft component being close to a Gaussian, and the hard component vanishing in the forward direction, while including the Rutherford asymptotics and all the power corrections to it at large scattering angles. Detailed properties of those components, and their interplay at intermediate deflection angles are discussed. Comparison with the Molière theory is given.

hep-ph↗

arXiv2015

Limiting Energy Loss Distributions for Multiphoton Channeling Radiation

Recent results in the theory of multiphoton spectra for coherent radiation sources are overviewed, with the emphasis on channeling radiation. For the latter case, the importance of the order of resummation and averaging is illustrated. Limiting shapes of multiphoton spectra at high intensity are discussed for different channeling regimes. In some spectral regions, there emerges an approximate correspondence between the radiative energy loss and the electron integrals of motion.

physics.acc-ph↗

arXiv2014

Interference Peak in the Spectrum of Bremsstrahlung on Two Amorphous Targets

We investigate the interference pattern in the spectrum of non-dipole bremsstrahlung on two amorphous foils. Apart from suppression at lowest $ω$, the spectrum exhibits an enhancement adjacent to it. In classical electrodynamics, the net effect of suppression and enhancement proves to be zero. We study the location and the origin of the spectral features, comparing predictions of full Molière averaging with those of the Gaussian averaging with Coulomb corrections to the rms multiple scattering angle. Comparison with experimental data, and with previous theoretical predictions is presented.

hep-ph↗

arXiv2013

Multiphoton effects in coherent radiation spectra

At measurements of gamma-radiation spectra from ultra-relativistic electrons in periodic structures, pileup of events in the calorimeter may cause significant deviation of the detector signal from the classically evaluated spectrum. That requires appropriate resummation of multiphoton contributions. We describe the resummation procedure for the photon spectral intensity and for the photon multiplicity spectrum, and apply it to the study of spectra of coherent radiation with an admixture of incoherent component. Impact of multiphoton effects on the shape of the radiation spectrum is investigated. The limit of high photon multiplicity for coherent radiation is explored. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is proposed.

physics.acc-ph↗

arXiv2013

Parameterization for qT-spectrum of inclusive Z-boson hadroproduction

We propose a simple parameterization for $q_T$-spectrum of inclusive $Z$-boson production, and test it against world collider data at different energies. The fit gives good agreement with the data, and indicates the existence of two distinguishable breaks in the $q_T$-spectrum. Energy dependences of the fitted parameters are discussed.

hep-ph↗

arXiv2011

Factorization and QCD Enhancements in the Compton Mechanism of W And Z Boson Hadroproduction

It is argued that $W/Z$ boson production in ultra-relativistic $pp$ collisions in the fragmentation region, subject to a kinematic cut on the boson transverse momentum $Q_\perp>Q_{\perp\min}$, with 1 GeV/c$\ll Q_{\perp\min}\ll M_{W/Z}$, must be dominated by the Compton mechanism $qg\to q'W/Z$. We propose applications for boson hadroproduction in this kinematics and formulate the factorization theorem. The analysis of QCD enhancements indicates that Regge behavior should manifest itself not only in the $s$ but also in $Q_\perp$-dependence of the boson production differential cross-section.

hep-ph↗

arXiv2011

Account of Nuclear Scattering at Volume Reflection

For a particle traversing a bent crystal in the regime of volume reflection we evaluate the probability of interaction with atomic nuclei. Regardless of the continuous potential shape, this probability is found to differ from the corresponding value in an amorphous target by an amount proportional to the crystal bending radius, and the particle deflection angle. Based on this result, we evaluate the rate of inelastic nuclear interactions, and the final beam angular dispersion due to multiple Coulomb scattering. The theoretical predictions are compared with the experiments. The impact of multiple Coulomb scattering on the mean volume reflection angle is also discussed.

physics.acc-ph↗

arXiv2011

Comments on theory of volume reflection and radiation in bent crystals

Recent theoretical results on charged particle interaction with planarly oriented thin bent crystals are reviewed, with the emphasis on dynamics in the continuous potential. Influence of boundary conditions on the volume-reflected beam profile is discussed. Basic properties of coherent bremsstrahlung in a bent crystal are highlighted.

physics.acc-ph↗

arXiv2010

Polarization of bremsstrahlung at electron scattering in an anisotropic medium

Bremsstrahlung from relativistic electrons is considered under conditions when some transverse direction of momentum transfer is statistically preferred. It is shown that in the dipole approximation all the medium anisotropy effects can be accumulated into a special modulus-bound transverse vector, $\bm N$. To exemplify a target with $N^2\sim1$, we calculate radiation from electron incident at a small angle on an atomic row in oriented crystal. Radiation intensity and polarization dependence on the emission angle and frequency for constant $\bm N$ is investigated. Net polarization for the angle-integral cross-section is evaluated, which appears to be proportional to $N^2/2$, and decreases with the increase of the photon energy fraction. A prominent feature of the radiation angular distribution is the existence of an angle at which the radiation may be completely polarized, in spite of the target complete or partial isotropy -- that owes to existence of an origin-centered tangential circle for polarization in the fully differential radiation probability kernel. Possibilities for utilizing various properties of the polarized bremsstrahlung flux for preparation of polarized photon beams and for probing intrinsic anisotropy of the medium are analyzed.

hep-ph↗

arXiv2010

Model solution for volume reflection of relativistic particles in a bent crystal

For volume reflection process in a bent crystal, exact analytic expressions for positively- and negatively-charged particle trajectories are obtained within a model of parabolic continuous potential in each interplanar interval, with the neglect of incoherent multiple scattering. In the limit of the crystal bending radius greatly exceeding the critical value, asymptotic formulas are obtained for the particle mean deflection angle in units of Lindhard's critical angle, and for the final beam profile. Volume reflection of negatively charged particles is shown to contain effects of rainbow scattering and orbiting, whereas with positively charged particles none of these effects arise within the given model. The model predictions are compared with experimental results and numerical simulations. Estimates of the volume reflection mean angle and the final beam profile robustness under multiple scattering are performed.

physics.class-ph↗

arXiv2010

Coherent bremsstrahlung in a bent crystal

Radiation spectrum from high energy $e^\pm$ in a bent crystal with arbitrary curvature distribution along the longitudinal coordinate is evaluated, based on the stationary phase approximation. For a uniformly bent crystal a closed-form expression for the spectrum is derived. Features such as sharp end of spectrum and volume reflection turnover at beginning of the spectrum are discussed. The coherence length in a bent crystal appears to depend only on the crystal geometry and not on the electron or photon energies, which is essential for interpretation of the results. Estimates of non-dipole radiation and multiple scattering effects are given. The value for the crystal bending angle at which the dipole coherent bremsstrahlung theory holds best appears to be $\sim 10^{-4}\mathrm{rad}$.

physics.acc-ph↗