arXiv subjects

A. I. Milstein

Publications and source records attributed to A. I. Milstein.

At least 55 records · Page 3Linked to original sources

arXiv2019

Consistent analysis of $f_1 (1285)$ meson form factors

Parameterization of the form factors of $f_1 (1285)$ meson is proposed. This parameterization is consistent with the available experimental data on the cross sections of $f_1 (1285)$ meson production in the processes $e^+e^- \to f_1 (1285)$ and $e^+e^- \to e^+e^-f_1 (1285)$, as well as on the widths of the decays $f_1 (1285)\to e^+e^-$, $f_1 (1285)\to ρ^0γ$, $f_1 (1285)\to ρ^0π^+π^-$, and $f_1 (1285)\to 2π^+2π^-$. Our parameterization is also consistent with the predictions for the asymptotic behavior of these form factors.

hep-ph↗

arXiv2019

Possibility to investigate P-parity violation in nuclear collisions at facility NICA

A possible experimental setup for measuring the effect of parity violation in the interaction of the polarized proton or deuteron beams with an unpolarized target is discussed. One possibility is investigation of scattering of the proton or deuteron polarized beams on a thick internal target in one of the rings of the NICA collider. In this case, the spin of a circulating particles is transformed into a mode precessing in the horizontal plane using an RF flipper. The effect of parity violation will be studied by measuring the correlation of the interaction cross section of particles and the direction of their spins. In an alternative approach, the flipper transforms the spins of particles into a horizontal plane and the beam is extracted into the channel in a certain phase of the precession. In this more traditional experimental setup, the total cross section of the passage of particles through a dense target is measured, depending on the sign of the helicity of the polarization of the beam.

hep-ex↗

arXiv2019

High-energy bremsstrahlung on atoms in a laser field

The impact of a laser field on the process of photon radiation by an ultra-relativistic electron in an atomic field is investigated. The angular distribution and the spectrum of the radiated photon are derived. By means of the quasiclassical approximation, the obtained results are exact in the parameters of the laser field and the atomic field. It is shown that the impact of the laser field is significant even for fairly average values of the laser field parameters routinely achievable nowadays. Therefore, an experimental observation of the influence of the laser field on bremsstrahlung in the atomic field is a very feasible task.

hep-ph↗

arXiv2018

Electron-electron interaction in graphene at finite Fermi energy

The wave equation describing the interaction of two electrons in graphene at arbitrary value of the Fermi energy $E_F$ is derived. For the solutions of this equation, we have found the explicit forms of the density and the current which obey the continuity equation. We have traced the evolution of the wave packet during a scattering process. It is shown that the long-leaving localized quasi-stationary peak may appear at $E_F<0$ . Then this peak decays into a set of wave packets following each other. At $t\rightarrow\infty$ a total norm of all outgoing wave packets equals to that of incoming wave packet. At $E_F=0$ the localized state does not appear. For $E_F<0$ there is an infinite set of the localized solutions with the finite norms.

cond-mat.mes-hall↗

arXiv2018

Fine structure of the cross sections of $e^{+}e^{-}$ annihilation near the thresholds of $p\bar{p}$ and $n\bar{n}$ production

The energy dependence of the cross sections of $p\bar p$, $n\bar n$, and meson production in $e^+e^-$ annihilation in the vicinity of the $p\bar p$ and $n\bar n$ thresholds is studied. The proton-neutron mass difference and the $p\bar p$ Coulomb interaction are taken into account. The values of the cross sections are very sensitive to the parameters of the optical potential. It is shown that the commonly accepted factorization approach for the account of the Coulomb interaction does not work well enough in the vicinity of the threshold due to the finite size of the optical potential well.

hep-ph↗

arXiv2017

High-energy $μ^+μ^-$ electroproduction

The cross sections of high-energy $μ^+μ^-$ pair production and paradimuonium production by a relativistic electron in the atomic field are discussed. The calculation is performed exactly in the parameters of the atomic field. Though the Coulomb corrections to the cross sections, related to the multiple Coulomb exchange of $μ^+,\,μ^-$ and an atom, are negligible, the Coulomb corrections to the differential cross sections, related to the electron interaction with an atom, are large. However, the latter Coulomb corrections to the cross sections integrated over the final electron momentum are small. Apparently, this effect can easily be observed experimentally. Furthermore, it is shown that the asymmetry of the cross section with respect to the permutation of the momenta of $μ^-$ and $μ^+$ is large.

hep-ph↗

arXiv2017

Integrated cross sections of high-energy $e^+e^-$ electroproduction by an electron in an atomic field

The integrated cross sections of high-energy $e^+e^-$ electroproduction by an electron in an atomic field is studied. Importance of various contributions to these cross sections is discussed. It is shown that the Coulomb corrections are very important both for the differential cross section and for the integrated cross sections even for moderate values of the atomic charge number. This effect is mainly related to the interaction of the produced $e^+e^-$ pair with the atomic field. For the cross section differential over the electron transverse momentum the account for the interference of the amplitudes and the contribution of virtual bremsstrahlung is noticeable. The Coulomb corrections to scattering is larger than these two effects but essentially smaller than the Coulomb corrections to the amplitude of pair photoproduction by a virtual photon. However, in the cross section differential over the positron transverse momentum, there is a strong suppression of the effect of the Coulomb corrections to scattering.

nucl-th↗

arXiv2017

Coulomb effects in high-energy $e^+e^-$ electroproduction by a heavy charged particles in an atomic field

The cross section of high-energy $e^+e^-$ pair production by a heavy charged particle in the atomic field is investigated in detail. We take into account the interaction with the atomic field of $e^+e^-$ pair and a heavy particle as well. The calculation is performed exactly in the parameters of the atomic field. It is shown that, in contrast to the commonly accepted point of view, the cross section differential with respect to the final momentum of a heavy particle is strongly affected by the interaction of a heavy particle with the atomic field. However, the cross section integrated over the final momentum of a heavy particle is independent of this interaction.

hep-ph↗

arXiv2017

Interaction of real and virtual $p\bar{p}$ pairs in $J/ψ\to p\bar{p}γ(ρ,ω)$ decays

The $p\bar{p}$ invariant mass spectra of the processes $J/ψ\to p\bar{p}ω$, $J/ψ\to p\bar{p}ρ$, and $J/ψ\to p\bar{p}γ$ close to the $p\bar{p}$ threshold are calculated by means of the $N\bar{N}$ optical potential. The potential model for $N\bar{N}$ interaction in the $^{1}S_{0}$ state is proposed. The parameters of the model are obtained by fitting the cross section of $N\bar{N}$ scattering together with the $p\bar{p}$ invariant mass spectra of the $J/ψ$ decays. Good agreement with the available experimental data is achieved. Using our potential and the Green's function approach we also describe the peak in the $η'π^{+}π^{-}$ invariant mass spectrum in the decay $J/ψ\toγη'π^{+}π^{-}$ in the energy region near the $N\bar{N}$ threshold.

hep-ph↗

arXiv2016

Electron-positron pair production in ion collisions at low velocity beyond Born approximation

We derive the spectrum and the total cross section of electromagnetic $e^{+}e^{-}$ pair production in the collisions of two nuclei at low relative velocity $β$. Both free-free and bound-free $e^{+}e^{-}$ pair production is considered. The parameters $η_{A,B}=Z_{A,B}α$ are assumed to be small compared to unity but arbitrary compared to $β$ ($Z_{A,B}$ are the charge numbers of the nuclei and $α$ is the fine structure constant). Due to a suppression of the Born term by high power of $β$, the first Coulomb correction to the amplitude appears to be important at $η_{A,B}\gtrsim β$. The effect of a finite nuclear mass is discussed. In contrast to the result obtained in the infinite nuclear mass limit, the terms $\propto M^{-2}$ are not suppressed by the high power of $β$ and may easily dominate at sufficiently small velocities.

physics.atom-ph↗

arXiv2016

Angular distributions in $J/ψ\to p\bar{p}π^{0}(η)$ decays

The differential decay rates of the processes $J/ψ\to p\bar{p}π^{0}$ and $J/ψ\to p\bar{p}η$ close to the $p\bar{p}$ threshold are calculated with the help of the $N\bar{N}$ optical potential. The same calculations are made for the decays of $ψ(2S)$. We use the potential which has been suggested to fit the cross sections of $N\bar{N}$ scattering together with $N\bar{N}$ and six pion production in $e^{+}e^{-}$ annihilation close to the $p\bar{p}$ threshold. The $p\bar{p}$ invariant mass spectra is in agreement with the available experimental data. The anisotropy of the angular distributions, which appears due to the tensor forces in the $N\bar{N}$ interaction, is predicted close to the $p\bar{p}$ threshold. This anisotropy is large enough to be investigated experimentally. Such measurements would allow one to check the accuracy of the model of $N\bar{N}$ interaction.

hep-ph↗

arXiv2016

High-energy electroproduction in an atomic field

The differential cross section of high-energy electroproduction in the electric field of heavy atoms is derived. The result is obtained with the exact account of the atomic field by means of the quasiclassical approximation to the wave functions in the external field. The Coulomb corrections substantially modify the differential cross section compared with the Born result. They lead to the azimuth asymmetry in the differential cross section for the polarized incoming electron. The Coulomb corrections to the total cross section are obtained in the leading logarithmic approximation.

hep-ph↗

arXiv2015

Real and virtual $N\bar{N}$ pair production near the threshold

Nucleon-antinucleon optical potential, which explains the experimental data for the processes $e^{+}e^{-}\rightarrow p\bar{p}$ and $e^{+}e^{-}\rightarrow\mbox{pions}$ near the threshold of $p\bar{p}$ pair production, is suggested. To obtain this potential we have used the available experimental data for $p\bar{p}$ scattering, $p\bar{p}$ pair production in $e^{+}e^{-}$ annihilation, and the ratio of electromagnetic form factors of a proton in the timelike region. It turns out that final-state interaction via the optical potential allows one to reproduce the available experimental data with good accuracy. Our results for the cross sections of $e^{+}e^{-}\to6π$ process near the threshold of $p\bar{p}$ pair production are in agreement with the recent experiments.

hep-ph↗

arXiv2015

Small-angle scattering and quasiclassical approximation beyond leading order

In the present paper we examine the accuracy of the quasiclassical approach on the example of small-angle electron elastic scattering. Using the quasiclassical approach, we derive the differential cross section and the Sherman function for arbitrary localized potential at high energy. These results are exact in the atomic charge number and correspond to the leading and the next-to-leading high-energy small-angle asymptotics for the scattering amplitude. Using the small-angle expansion of the exact amplitude of electron elastic scattering in the Coulomb field, we derive the cross section and the Sherman function with a relative accuracy $θ^2$ and $θ^1$, respectively ($θ$ is the scattering angle). We show that the correction of relative order $θ^2$ to the cross section, as well as that of relative order $θ^1$ to the Sherman function, originates not only from the contribution of large angular momenta $l\gg 1$, but also from that of $l\sim 1$. This means that, in general, it is not possible to go beyond the accuracy of the next-to-leading quasiclassical approximation without taking into account the non-quasiclassical terms.

physics.atom-ph↗

arXiv2015

Double bremsstrahlung from high-energy electron in the atomic field

The differential cross section of double bremsstrahlung from high-energy electron in the electric field of heavy atoms is derived. The results are obtained with the exact account of the atomic field by means of the quasiclassical approximation to the wave functions and the Green's function in the external field. It is shown that the Coulomb corrections to the differential cross section (the difference between the exact result and the result obtained in the leading Born approximation) correspond to small momentum transfers. The Coulomb corrections to the differential cross section of double bremsstrahlung are accumulated in the factor, which coincides with the corresponding factor in the differential cross section of single bremsstrahlung. At small momentum transfer, this factor is very sensitive to the parameters of screening while the Coulomb corrections to the spectrum have the universal form.

hep-ph↗

arXiv2015

Charge asymmetry in the differential cross section of high-energy bremsstrahlung in the field of a heavy atom

The distinction between the charged particle and antiparticle differential cross sections of high-energy bremsstrahlung in the electric field of a heavy atom is investigated. The consideration is based on the quasiclassical approximation to the wave functions in the external field. The charge asymmetry (the ratio of the antisymmetric and symmetric parts of the differential cross section) arises due to the account for the first quasiclassical correction to the differential cross section. All evaluations are performed with the exact account of the atomic field. We consider in detail the charge asymmetry for electrons and muons. For electrons, the nuclear size effect is not important while for muons this effect should be taken into account. For the longitudinal polarization of the initial charged particle, the account for the first quasiclassical correction to the differential cross section leads to the asymmetry in the cross section with respect to the replacement $φ\rightarrow-φ$, where $φ$ is the azimuth angle between the photon momentum and the momentum of the final charged particle.

hep-ph↗

arXiv2014

High-energy $e^+e^-$ photoproduction in the field of a heavy atom accompanied by bremsstrahlung

Helicity amplitudes and differential cross section of high-energy $e^+e^-$ photoproduction accompanied by bremsstrahlung in the electric field of a heavy atom are derived. The results are exact in the nuclear charge number and obtained in the leading quasiclassical approximation. They correspond to the leading high-energy small-angle asymptotics of the amplitude. It is shown that, in general, the Coulomb corrections essentially modify the differential cross section as compared to the Born result. When the initial photon is circularly polarized the Coulomb corrections lead to the asymmetry in the distribution over the azimuth angles $φ_i$ of produced particles with respect to the replacement $φ_i\to -φ_i$.

hep-ph↗

arXiv2014

Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields

The problem of an ultrarelativistic charge in the presence of an atomic and a plane-wave field is investigated in the quasiclassical regime by including exactly the effects of both background fields. Starting from the quasiclassical Green's function obtained in [Phys. Lett. B \textbf{717}, 224 (2012)], the corresponding in- and out-wave functions are derived in the experimentally relevant case of the particle initially counterpropagating with respect to the plane wave. The knowledge of these electron wave functions opens the possibility of investigating a variety of problems in strong-field QED, where both the atomic field and the laser field are strong enough to be taken into account exactly from the beginning in the calculations.

hep-ph↗