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A. E. Kudryavtsev

Publications and source records attributed to A. E. Kudryavtsev.

53 records · Page 3Linked to original sources
arXiv2002

Production of eta mesons in nucleon-nucleon collisions

A microscopic calculation of near-threshold eta-meson production in the reaction NN -> NNeta is presented. It is assumed that the eta meson is produced via direct emission and via elementary rescattering processes MN -> etaN of various mesons M = pi, rho, etc. As a novel feature the amplitudes for the latter production mechanism are taken from a multi-channel meson-exchange model of the pi N system developed by the Juelich group which contains explicitly the channels pi N, rho N, eta N, sigma N, and pi Delta. Furthermore, effects of the NN interaction in the final as well as in the initial state are taken into account microscopically. Our results are compared with recent data from the COSY and CELSIUS accelerator facilities. Reasonable agreement with available near-threshold cross section data for the reactions pp -> ppeta, pn -> pneta, and pn -> deta is found.

nucl-th↗
arXiv2002

The Centauro events as a result of induced pions emission

It is shown that only in the case of n pion production amplitude (at n > 10), which is symmetric enough relative to the momenta permutations, there is appreciable probability of events with nothing but charged or nothing but neutral pions. Significant enhancement of the probability of these events in comparison with that follows from Poisson distribution is caused by induced pions emission, in complete analogy with the phenomenon of the induced photon emission in QED.

hep-ph↗
arXiv2002

Perturbative approach to the hydrogen atom in strong magnetic field

The states of hydrogen atom with principal quantum number n <= 3 and zero magnetic quantum number in constant homogeneous magnetic field H are considered. The perturbation theory series is summed with the help of Borel transformation and conformal mapping of the Borel variable. Convergence of approximate energy eigenvalues and their agreement with corresponding existing results are observed for external fields up to n^3 H ~ 5. The possibility of restoring the asymptotic behaviour of energy levels using perturbation theory coefficients is also discussed.

physics.atom-ph↗
arXiv2002

Aspects of a0-f0 mixing in the reaction pn->da0

Some aspects of a0-f0 mixing effects in the reaction ${\vec p} n\to da^0_0$ with perpendicular polarized proton beam are discussed. An angular--asymmetry parameter $A$ is defined to study those effects. It is shown that, for energies close to the production threshold, the angular--asymmetry parameter $A(θ, ϕ)$ is proportional to the a0-f0 mixing amplitude for arbitrary polar and azimuthal angles $θ$ and $ϕ$ of the outgoing $a_0$ meson. This statement is also valid for arbitrary energies, but then only at polar angles $θ=0^0$ and $θ=90^0$. The mass dependence of the differential cross section $dσ/dm_{π^0η}$ in the reaction $pn\to dπ^0η$ in the presence of \mix mixing is also discussed.

nucl-th↗
arXiv2001

Charge-Symmetry Violation in Pion Scattering from Three-Body Nuclei

We discuss the experimental and theoretical status of charge-symmetry violation (CSV) in the elastic scattering of pi+ and pi- on 3H and 3He. Analysis of the experimental data for the ratios r1, r2, and R at Tpi = 142, 180, 220, and 256 MeV provides evidence for the presence of CSV. We describe pion scattering from the three-nucleon system in terms of single- and double-scattering amplitudes. External and internal Coulomb interactions as well as the Delta-mass splitting are taken into account as sources of CSV. Reasonable agreement between our theoretical calculations and the experimental data is obtained for Tpi = 180, 220, and 256 MeV. For these energies, it is found that the Delta-mass splitting and the internal Coulomb interaction are the most important contributions for CSV in the three-nucleon system. The CSV effects are rather sensitive to the choice of pion-nuclear scattering mechanisms, but at the same time, our theoretical predictions are much less sensitive to the choice of the nuclear wave function. It is found, however, that data for r2 and R at Tpi = 142 MeV do not agree with the predictions of our model, which may indicate that there are additional mechanisms for CSV which are important only at lower energies.

nucl-th↗
arXiv2001

On U(1)-charged domain walls

A classical field system of two interacting fields -- a real Higgs field and a complex scalar field -- is considered. It is shown that in such field system a non-trivial solution exists, which is U(1) charged topological kink. Some questions of stability of the obtained solution are discussed. An improved variational procedure for searching of topological U(1) charged solutions is given.

hep-th↗
arXiv2001

On the possibility of observation of $a_0$-$f_0$ mixing in the $pn \to da_0$ reaction

It is shown that, if isospin is not conserved in $a^0_0$- and $f_0$-meson mixing, forward-backward asymmetry arises in the reaction $pn\to da^0_0$. This effect increases near the reaction threshold. The asymmetry is estimated within the framework of a model in which the $a^0_0$-$f_0$ mixing is due to the virtual $π^0\leftrightarrowη$ transition and the difference in masses of the charged and neutral kaons in decay channels. The angular asymmetry near the threshold of the $pn\to da^0_0$ reaction was found to be large, of the order of $8÷15$ %.

nucl-th↗
arXiv2000

On the Migdal-Watson approach to FSI effects in meson production in NN collisions

The influence of the nucleon-nucleon final state interaction (FSI) on properties of the meson production amplitude near threshold is discussed. For the nucleon-nucleon interaction a simple Yamaguchi potential as well as realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like eta' or phi FSI effects become universal. The Jost function approach to FSI effects is critically examined.

nucl-th↗
arXiv2000

On decay of large amplitude bubble of disoriented chiral condensate

The time evolution of initially formed large amplitude bubble of disoriented chiral condensate (DCC) is studied. It is found that the evolution of this object may have a relatively long pre-decay stage. Simple explanation of such delay of the DCC bubble decay is given. This delay is related to the existence of the approximate solutions of multi-soliton type of the corresponding radial sine-Gordon equation in (3+1) dimensions at large bubble radius.

hep-ph↗
arXiv2000

Charge Symmetry Violation Effects in Pion Scattering off the Deuteron

We discuss the theoretical and experimental situations for charge symmetry violation (CSV) effects in the elastic scattering of pi+ and pi- on deuterium (D) and 3He/3H. Accurate comparison of data for both types of targets provides evidence for the presence of CSV effects. While there are indications of a CSV effect in deuterium, it is much more pronounced in the case of 3He/3H. We provide a description of the CSV effect on the deuteron in terms of single- and double- scattering amplitudes. The Delta-mass splitting is taken into account. Theoretical predictions are compared with existing experimental data for pi-d scattering; a future article will speak to the pi-three nucleon case.

nucl-th↗
arXiv1999

Some comments on $\bar n p$-annihilation branching ratios into $ππ$-, $\bar K K$- and $πη$-channels

We give some remarks on the $\bar n p$-partial branching ratios in flight at low momenta of antineutron, measured by OBELIX collaboration. The comparison is made to the known branching ratios from the $p \bar p$-atomic states. The branching ratio for the reaction $\bar n p \to π^+π^0$ is found to be suppressed in comparison to what follows from the $ p \bar p$-data. It is also shown, that there is no so called dynamic I=0-amplitude suppression for the process $N\bar N \to K\bar K$.

hep-ph↗
arXiv1999

On the interactions of Skyrmions with domain walls

We study classical solutions of a particular version of the modified Skyrme model in (3+1) dimensions. The model possesses Skyrmion solutions as well as stable domain walls that connect different vacua of the theory. We show that there is an attractive interaction between Skyrmions and domain walls. Thus Skyrmions can be captured by the domain walls. We show also that, when the mass term is of a special type, the model possesses bound states of Skyrmions and of the domain wall. They look like deformed 2-dimensional Skyrmions captured by the wall. The field configurations of these solutions can interpreted as having come from the evolution of the 3-dimensional Skyrmions captured by the domain wall. For more conventional choices of the mass term of the model in the model the attraction between the Skyrmions and the wall leads to the capture of the Skyrmions which are then turned into topological waves which spread out on the wall. We have observed, numerically, such captures and the emission of the waves. We speculate that this observation may be useful in the explanation of the problem of baryogenesis and baryon-antibaryon asymmetry of the Universe.

hep-th↗
arXiv1999

A remark on collisions of domain walls in a supersymmetric model

The process of collision of two parallel domain walls in a supersymmetric model is studied both in effective Lagrangian approximation and by numerical solving of the exact classical field problem. For small initial velocities we find that the walls interaction looks like elastic reflection with some delay. It is also shown that in such approximation internal parameter of the wall may be considered as a time-dependent dynamical variable.

hep-th↗
arXiv1998

Kink-antikink interactions in the double sine-Gordon equation and the problem of resonance frequencies

We studied the kink-antikink collision process for the "double sine-Gordon" (DSG) equation in 1+1 dimensions at different values of the potential parameter $R>0$. For small values of $R$ we discuss the problem of resonance frequencies. We give qualitative explanation of the frequency shift in comparison with the frequency of the discrete level in the potential well of isolated kink. We show that in this region of the parameter $R$ the effective long-range interaction between kink and antikink takes place.

cond-mat↗
arXiv1998

On decay of bubble of disoriented chiral condensate

We discuss the space-time structure for the process of decay of a bubble of hypothetic phase -- disoriented chiral condensate (DCC). The evolution of the initial classical field configuration corresponding to the bubble of DCC is studied both numerically and analytically. The process of decay of this initial configuration depends crucially on selfinteraction of the pionic fields. It is shown that in some cases this selfinteraction leads to the formation of sort of breather solution, formed from pionic fields situated in the center of the initial bubble of DCC. This breather looks like a long-lived source of pionic fields.

hep-ph↗
arXiv1997

High orders of the perturbation theory for hydrogen atom in magnetic field

The states of hydrogen atom with principal quantum number $n\le3$ and zero magnetic quantum number in constant homogeneous magnetic field ${\cal H}$ are considered. The coefficients of energy eigenvalues expansion up to 75th order in powers of ${\cal H}^2$ are obtained for these states. The series for energy eigenvalues and wave functions are summed up to ${\cal H}$ values of the order of atomic magnetic field. The calculations are based on generalization of the moment method, which may be used in other cases of the hydrogen atom perturbation by a polynomial in coordinates potential.

physics.atom-ph↗