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A. S. Rudenko

Publications and source records attributed to A. S. Rudenko.

At least 19 recordsLinked to original sources
arXiv2025

Charge asymmetry in the process $e^+e^-\to \pi^+\pi^-\pi^0\gamma$

The charge asymmetry in the process $e^+e^-\to \pi^+\pi^-\pi^0\gamma$ is studied for photons with energies $\nu\ll\sqrt{s}$. The longitudinal polarization of electrons (positrons) is taken into account. The asymmetry arises due to interference of the amplitudes for production of pion states with opposite $C$ parities. The contribution of $a_1^0(1260)$ meson in the intermediate state to the charge asymmetry is discussed. This contribution is not the leading one, however it is not negligible. It is shown that the charge asymmetry can reach several tens of percent.

hep-ph↗
arXiv2024

Manifestation of $a_1(1260)$ meson in the process $e^+e^-\to π^+π^-π^0$

The charge asymmetry in the process $e^+e^-\to π^+π^-π^0$ is studied taking into account a longitudinal polarization of electrons (positrons). The asymmetry arises due to interference of amplitudes corresponding to production of pions in C-odd and C-even states. It is a manifestation of $a_1(1260)$ meson in the intermediate state. Polarization leads to additional correlations in the differential cross section, which simplifies the experimental study of the process. It is shown that the charge asymmetry can reach several percent.

hep-ph↗
arXiv2024

Conversion of protons to positrons by a black hole

The conversion of protons to positrons at the horizon of a black hole (BH) is considered. It is shown that the process may efficiently proceed for BHs with masses in the range $\sim 10^{18}$ -- $10^{21}$ g. It is argued that the electric charge of BH acquired by the proton accretion to BH could create electric field near BH horizon close to the critical Schwinger one. It leads to efficient electron-positron pair production, when electrons are back captured by the BH while positrons are emitted into outer space. Annihilation of these positrons with electrons in the interstellar medium may at least partially explain the origin of the observed 511 keV line.

hep-ph↗
arXiv2024

Gravitational four-fermion interaction and dynamics of the early Universe

If torsion exists, it generates gravitational four-fermion interaction (GFFI), essential on the Planck scale. We analyze the influence of this interaction on the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology. Explicit analytical solution is derived for the problem where both the energy-momentum tensor generated by GFFI and the common ultrarelativistic energy-momentum tensor are included. We demonstrate that gravitational four-fermion interaction does not result in Big Bounce.

astro-ph.CO↗
arXiv2024

Cosmology constrains gravitational four-fermion interaction

If torsion exists, it generates gravitational four-fermion interaction (GFFI). This interaction gets dominating on the Planck scale. If one confines to the regular, axial-axial part of this interaction, the results do not comply with the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology for the spatial flat or closed Universe. In principle, the anomalous, vector-vector interaction could restore the agreement.

astro-ph.CO↗
arXiv2023

Calculations of scalaron decay probabilities

The particle production through the scalaron decays are considered for several different channels. The central part of the work is dedicated to a study of the decay probability into two complex minimally coupled massless scalars. The calculations are performed by two different independent methods. In addition we calculated the decay probability into real minimally coupled massless scalars, conformally coupled massive scalars, massive fermions, and gauge bosons. The results are compared with the published papers which in some cases disagree with each other.

hep-ph↗
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↗
arXiv2018

Evolution of thick domain walls in inflationary and $p=wρ$ universe

We study the evolution of thick domain walls in the different models of cosmological inflation, in the matter-dominated and radiation-dominated universe, or more generally in the universe with the equation of state $p=wρ$. We have found that the domain wall evolution crucially depends on the time-dependent parameter $C(t)=1/(H(t)δ_0)^2$, where $H(t)$ is the Hubble parameter and $δ_0$ is the thickness of the wall in flat space-time. For $C(t)>2$ the physical thickness of the wall, $a(t)δ(t)$, tends with time to $δ_0$, which is microscopically small. Otherwise, when $C(t) \leq 2$, the wall steadily expands and can grow up to a cosmologically large size.

gr-qc↗
arXiv2017

$f_1 (1285) \to e^+e^-$ decay and direct $f_1$ production in $e^+e^-$ collisions

The width of the $f_1 (1285) \to e^+e^-$ decay is calculated in the vector meson dominance model. The result depends on the relative phase between two coupling constants describing $f_1 \to ρ^0γ$ decay. The width $Γ(f_1 \to e^+e^-)$ is estimated to be $\simeq 0.07-0.19$ eV. Direct $f_1$ production in $e^+e^-$ collisions is discussed, and the $e^+e^- \to f_1\to a_0 π\to ηππ$ cross section is calculated. Charge asymmetry in the $e^+e^- \to ηπ^+ π^-$ reaction due to interference between $e^+e^- \to f_1$ and $e^+e^- \to ηρ^0$ amplitudes is studied.

hep-ph↗
arXiv2017

Relic abundance of MeV millicharged particles

The relic abundance of light millicharged particles (MCPs) with the electric charge $e' = 5\cdot 10^{-5} e$ and with the mass slightly below or above the electron mass is calculated. The abundance depends on the mass ratio $η=m_X/m_e$ and for $η<1$ can be high enough to allow MCPs to be the cosmological dark matter or to make a noticeable contribution to it. On the other hand, for $η\gtrsim 1$ the cosmological energy density of MCPs can be quite low, $Ω_X h_0^2 \approx 0.02$ for scalar MCPs, and $Ω_X h_0^2 \approx 0.001$ for spin 1/2 fermions. But even the lowest value of $Ω_X h_0^2$ is in tension with several existing limits on the MCP abundances and parameters. However, these limits have been derived under some natural or reasonable assumptions on the properties of MCPs. If these assumptions are relaxed, a patch in the mass-charge plot of MCPs may appear, permitting them to be dark matter particles.

hep-ph↗
arXiv2016

Evolution of thick domain walls in de Sitter universe

We consider thick domain walls in a de Sitter universe following paper by Basu and Vilenkin. However, we are interested not only in stationary solutions found therein, but also investigate the general case of domain wall evolution with time. When the wall thickness parameter, $δ_0$, is smaller than $H^{-1}/\sqrt{2}$, where $H$ is the Hubble parameter in de Sitter space-time, then the stationary solutions exist, and initial field configurations tend with time to the stationary ones. However, there are no stationary solutions for $δ_0 \geq H^{-1}/\sqrt{2}$. We have calculated numerically the rate of the wall expansion in this case and have found that the width of the wall grows exponentially fast for $δ_0 \gg H^{-1}$. An explanation for the critical value $δ_{0c} = H^{-1}/\sqrt{2}$ is also proposed.

gr-qc↗
arXiv2015

Separated matter and antimatter domains with vanishing domain walls

We present a model of spontaneous (or dynamical) C and CP violation where it is possible to generate domains of matter and antimatter separated by cosmologically large distances. Such C(CP) violation existed only in the early universe and later it disappeared with the only trace of generated baryonic and/or antibaryonic domains. So the problem of domain walls in this model does not exist. These features are achieved through a postulated form of interaction between inflaton and a new scalar field, realizing short time C(CP) violation.

astro-ph.CO↗
arXiv2015

Shape of the inflaton potential and the efficiency of the universe heating

It is shown that the efficiency of the universe heating by an inflaton field depends not only on the possible presence of parametric resonance in the production of scalar particles but also strongly depends on the character of the inflaton approach to its mechanical equilibrium point. In particular, when the inflaton oscillations deviate from pure harmonic ones toward a succession of step functions, the production probability rises by several orders of magnitude. This in turn leads to a much higher temperature of the universe after the inflaton decay, in comparison to the harmonic case. An example of the inflaton potential is presented which creates a proper modification of the evolution of the inflaton toward equilibrium and does not destroy the nice features of inflation.

astro-ph.CO↗
arXiv2013

$K^0_{l3γ}$ decays: branching ratios and T-odd momenta correlations

The branching ratios of the $K^0 \to π^- l^+ ν_l γ(l = e, μ)$ decays, and the T-odd triple momenta correlations $ξ=\vec{q}\cdot[\vec{p}_l \times \vec{p}_π]/M^3_K$, due to the electromagnetic final state interaction, in these processes are calculated. The contributions on the order of $ω^{-1}$ and $ω^0$ to the corresponding amplitudes are treated exactly. For the branching ratios and T-odd correlation in $K^0 \to π^- e^+ ν_e γ$ decay, the corrections on the order of $ω$ are estimated and demonstrated to be small. The results for the branching ratios are in good agreement with the previous ones. The T-odd triple momenta correlations in $K^0_{l3γ}$ decays are calculated for the first time. The values of the ξ-odd asymmetry constitute $-1\times10^{-4}$ and $-4.5\times10^{-4}$ in the $K^0 \to π^- μ^+ ν_μγ$ and $K^0 \to π^- e^+ ν_eγ$ decays, respectively.

hep-ph↗
arXiv2011

Upper Limits on Electric and Weak Dipole Moments of W-Boson

The total cross-sections of the reaction e+e- --> W+W-, as measured at LEP-II at centre-of-mass energies between 183 and 207 GeV are used to derive the upper limits on the parameters of CP-violating (P-odd and C-even) triple gauge-boson couplings WWγand WWZ. The 95% CL limits |\widetildeκ_Z|<0.13 and |\widetildeλ_Z|<0.31 are obtained assuming local SU(2)_L x U(1)_Y gauge invariance. Our results are comparable with the previous ones obtained through the analysis of the W decay products. We also discuss the upper limits on the electric dipole moment (EDM) of the W-boson, which follow from the precision measurements of the electron and neutron EDM.

hep-ph↗
arXiv2010

$K^+_{l3γ}$ decays revisited: branching ratios and T-odd momenta correlations

We calculate the branching ratios of the $K^+ \to π^0 l^+ ν_lγ(l = e, μ)$ decays, and the T-odd triple momenta correlations $ξ=\vec{q}\cdot[\vec{p}_l \times \vec{p}_π]/M^3_K$, due to the electromagnetic final state interaction, in these processes. The contributions on the order of $ω^{-1}$ and $ω^0$ to the corresponding amplitudes are treated exactly. For the branching ratios, the corrections on the order of $ω$ are estimated and demonstrated to be small. We compare the results with those of other authors. In some cases our results differ considerably from the previous ones.

hep-ph↗