arXiv subjects

E. G. Drukarev

Publications and source records attributed to E. G. Drukarev.

At least 37 records · Page 2Linked to original sources

arXiv2013

Multielectron processes in endohedral atoms at high energies

We analyze the role of shake-off and of the final state interactions in inelastic processes in the fullerene shell which follow ionization of the caged atom. We demonstrate that in the broad interval of the photon energies the process is dominated by the final state interactions. Its contribution is calculated in a model-independent way. In the large energy intervals the cross section of the process is close to that of photoionization of isolated atom.

physics.atom-ph↗

arXiv2013

On the interactions of the high energy photoelectrons with the fullerene shell

The probability that photoionization of the caged atom in an endohedral system is accompanied by excitation of the fullerene shell is shown to be close to unity in broad intervals of the photoelectron energies. The result is obtained by summation of the perturbative series for the interaction between the photoelectron and the fullerene shell. This result means that the interaction between the photoelectron ejected from the cage atom and the fullerene shell cannot be described by a static potential, since inelastic processes become decisively important.

physics.atom-ph↗

arXiv2012

A New Approach to Physics of Nuclei

We employ the QCD sum rules method for description of nucleons in nuclear matter. We show that this approach provides a consistent formalism for solving various problems of nuclear physics. Such nucleon characteristics as the Dirac effective mass $m^*$ and the vector self-energy $Σ_V$ are expressed in terms of the in-medium values of QCD condensates. The values of these parameters at saturation density and the dependence on the baryon density and on the neutron-to-proton density ratio is in agreement with the results, obtained by conventional nuclear physics method. The contributions to $m^*$ and $Σ_V$ are related to observables and do not require phenomenological parameters. The scalar interaction is shown to be determined by the pion--nucleon $σ$-term. The nonlinear behavior of the scalar condensate may appear to provide a possible mechanism of the saturation. The approach provided reasonable results for renormalization of the axial coupling constant, for the contribution of the strong interactions to the neutron--proton mass difference and for the behavior of the structure functions of the in-medium nucleon. The approach enables to solve the problems which are difficult or unaccessible for conventional nuclear physics methods. The method provides guide-lines for building the nuclear forces. The three-body interactions emerge within the method in a natural way. There rigorous calculation will be possible in framework of self-consistent calculation in nuclear matter of the scalar condensate and of the nucleon effective mass $m^*$.

nucl-th↗

arXiv2012

The role of the in-medium four-quark condensates revised

We calculate the nucleon self-energies in nuclear matter in the QCD sum rules approach, taking into account the contributions of the four-quark condensates. We analyze the dependence of the results on the model employed for the calculation of the condensates and demonstrate that the relativistic character of the models is important. The condensates are calculated with inclusion of the most important terms beyond the gas approximation. This corresponds to inclusion of the two-body nucleon forces and of the most important three-body forces. The results are consistent with the convergence of the operator product expansion. The density dependence of the nucleon self-energies is obtained. The results are consistent with those obtained by the standard nuclear physics methods, thus inspiring further development of the approach.

nucl-th↗

arXiv2011

Back-to-back emission of the electrons in double photoionization of helium

We calculate the double differential distributions and distributions in recoil momenta for the high energy non-relativistic double photoionization of helium. We show that the results of recent experiments is the pioneering experimental manifestation of the quasifree mechanism for the double photoionization, predicted long ago in our papers. This mechanism provides a surplus in distribution over the recoil momenta at small values of the latter, corresponding to nearly "back-to-back" emission of the electrons. Also in agreement with previous analysis the surplus is due to the quadrupole terms of the photon-electron interaction. We present the characteristic angular distribution for the "back-to-back" electron emission. The confirmation of the quasifree mechanism opens a new area of exiting experiments, which are expected to increase our understanding of the electron dynamics and of the bound states structure. The results of this Letter along with the recent experiments open a new field for studies of two-electron ionization not only by photons but by other projectiles, e.g. by fast electrons or heavy ions.

physics.atom-ph↗

arXiv2009

Role of unphysical solution in nucleon QCD sum rules

We show that at certain values of QCD condensates the nucleon QCD sum rules with "pole+continuum" model for the hadron spectrum obtain an unphysical solution. This provides constrains for the values of condensates to be consistent with existence of a physical solutions. The constrains become much weaker if the radiative corrections are included perturbatively. We demonstrate that the most important dependence of nucleon mass on the quark scalar condensate becomes much weaker under factorization assumption for the four-quark and six-quark condensates.

nucl-th↗

arXiv2009

Nucleon QCD sum rules in nuclear matter including radiative corrections

We calculate the nucleon parameters in nuclear matter using the QCD sum rules method. The radiative corrections to the leading operator product expansion terms are included, with the corrections of the order α_s beyond the logarithmic approximation taken into account. The density dependence of the influence of radiative corrections on the nucleon parameters is obtained. At saturation density the radiative corrections increase the values of vector and scalar self-energies by about 40 MeV, and 30 MeV correspondingly. The results appear to be stable with respect to possible variations of the value of Λ_{QCD}.

nucl-th↗

arXiv2009

Particle cancellation of correlations in nonrelativistic high energy asymptotics of photoeffect

We investigate the total effect of correlations on photoionization of atomic shells with nonzero orbital momentum, in the nonrelativistic high energy asymptotic limit, considering the exclusive case of the dominant final state of an initial neutral atom. We find that the substantial cancellation of the dominant intra-shell carrelations, which had been reported earlier, can be understood utilizing the closure properties satisfied by the eigen functions of the nonrelativistic Hamiltonian. Considering the sum of correlations with all states, occupied or not, we show that complete sum is equal to the contribution of the high energy part of the continuum. Consequently there is a total cancellation between the contributions of the bound states and the low energy part of the continuum states. This means that the real correlations in the physical atom can be obtained as the negative of the total contribution of low energy states and continuum unoccupied states. We calculate this in framework of the quantum defect number. The approach allows us to see that the dominant intrashell correlation is going to be cancelled. We can also obtain some limits on the correlation effects by considering calculations with the screened Coulomb functions. The role of correlations in the exclusive photoionization processes is discussed.

quant-ph↗

arXiv2007

Triple coalescence singularity in a dynamical atomic process

We show that the high energy limit for the amplitude of the double electron capture to the bound state of the Coulomb field of a nucleus with emission of a single photon is determined by behavior of the wave function in the vicinity of the singular triple coalescence point.

quant-ph↗

arXiv2007

Photoionization accompanied by excitation at intermediate photon energies

We calculate the photoionization with excitation-to photoionization ratios for atomic helium and heliumlike ions at intermediate values of the photon energies. The final state interactions between the electrons are included in the lowest order of their Sommerfeld parameter. This enables us, in contrast to purely numerical calculations to investigate the roles of various mechanisms contributing beyond the high energy limit. The system of the two bound electrons is described by the functions obtained by the Correlation Function Hyperspherical Harmonic Method. For the case of heliumlike ions we present the high energy limits as power expansion in inverse charge of the nucleus. We analyse the role of excitation of states with the nonzero orbital momenta.

quant-ph↗

arXiv2007

Highly Accurate Analytic Presentation of Solution of the Schrödinger Equation

High-precision approximate analytic expressions for energies and wave functions are found for arbitrary physical potentials. The Schrödinger equation is cast into nonlinear Riccati equation, which is solved analytically in first iteration of the quasi-linearization method (QLM). The zeroth iteration is based on general features of the exact solution near the boundaries. The approach is illustrated on the Yukawa potential. The results enable accurate analytical estimates of effects of parameter variations on physical systems.

math-ph↗

arXiv2006

Nucleon sum rules in symmetric and asymmetric nuclear matter

We calculate the nucleon parameters in isospin symmetric and asymmetric nuclear matter using the QCD sum rules. The higher moments of the nucleon structure functions are included. The complete set of the nucleon expectation values of the four-quark operators is employed. We analyze the role of the lowest order radiative corrections beyond the logarithmic approximation.

nucl-th↗

arXiv2006

Formation of ions by high energy photons

We calculate the electron energy spectrum of ionization by a high energy photon, accompanied by creation of electron-positron pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energies. At the photon energies exceeding a certain value $ω_0$ this appeares to to be the dominant mechanism of formation of the ions. The dependence of $ω_0$ on the value of nuclear charge is obtained. Our results are consistent with experimental data.

quant-ph↗

arXiv2005

Nucleon QCD sum rules with the radiative corrections

QCD sum rules for the nucleon are considered in complex q^2 plane with inclusion of the radiative corrections of the order alpha_s. It is shown that the radiative corrections affect mainly the residue lambda^2 of the nucleon pole. Their influence on the value of the nucleon mass is much smaller. Following the ideas of Ioffe and Zyablyuk we expand the analysis to complex values of q^2. This provides a more stable solution. Varying the weights of the contributions of different dimensions by changing the value of the angle in the complex plane we find the value of the six-quark condensate which insures the best consistency of the right hand sides and left hand sides of the sum rules. The corresponding value of the six-quark condensate appears to be only about 10% smaller then the one, provided by the factorization approximation. The value of the four-quark condensate also appears to be close to the one, corresponding to the factorization assumption. The role of the gluon condensate and its possible values are discussed.

hep-ph↗

arXiv2004

Nucleon QCD sum rules in nuclear matter including four-quark condensates

We calculate the nucleon parameters in nuclear matter using the QCD sum rules approach in Fermi gas approximation. Terms up to 1/q^2 in the operator product expansion (OPE) are taken into account. The higher moments of the nucleon structure functions are included. The complete set of the nucleon expectation values of the four-quark operators is employed. Earlier the lack of information on these values has been the main obstacle for the further development of the approach. We show that the four-quark condensates provide the corrections of the order 20% to the results obtained in the leading orders of the OPE. This is consistent with the assumption about the convergence of the OPE. The nucleon vector self-energy Σ_v and the nucleon effective mass m^* are expressed in terms of the in-medium values of QCD condensates. The numerical results for these parameters at the saturation value of the density agree with those obtained by the methods of nuclear physics.

nucl-th↗

arXiv2004

QCD Sum Rules Description of Nucleons in Asymmetric Nuclear Matter

We calculate the nucleon parameters in isospin asymmetric nuclear matter using the QCD sum rules. The nucleon self-energies are expressed in terms of the in-medium values of QCD condensates. The simple approximate expressions for the self-energies are obtained in terms of these condensates. Relation between successive inclusion of the condensates and the meson-exchange picture of the nucleon interaction with medium is analyzed. The values of the self-energies and of the symmetry energy agree with those obtained by the methods of nuclear physics.

nucl-th↗

arXiv2004

Atomic physics: computer calculations and theoretical analysis

It is demonstrated, how the theoretical analysis preceding the numerical calculations helps to calculate the energy of the ground state of helium atom, and enables to avoid qualitative errors in the calculations of the characteristics of the double photoionization.

physics.atom-ph↗

arXiv2003

Expectation values of four-quark operators in the nucleon

We calculate expectation values of QCD operators consisting of the products of the four operators of the light quarks corresponding to the scalar, pseudoscalar, vector, pseudovector (axial) and tensor Lorentz structures in the nucleon. All combinations of the light flavors are considered. For the evaluation we use elements of the Perturbative Chiral Quark Model (PCQM), approximating the contribution of the valence quarks by the contribution of the PCQM constituent quarks. The contribution of the sea quarks is treated by averaging over the QCD pions with the distribution of the pion field being determined by the PCQM. For quarks with the same flavor the expectation values are dominated by the contribution of the sea-quarks. In the scalar case the contribution of the sea quarks is dominated by the "disconnected terms" were one of the pairs of the quark operators acts on the vacuum while the other one acts on the quarks of the pion. The role of the interference terms with one of the quark pairs acting on the sea quarks and another one acting on the valence quarks increases for quarks with different flavors. The result for the scalar condensate is compared to the one obtained earlier in the framework of the Nambu -Jona-Lasinio model.

hep-ph↗