arXiv subjects

M. K. Volkov

Publications and source records attributed to M. K. Volkov.

At least 37 records · Page 2Linked to original sources

arXiv2021

Calculation of the width of the decay $τ\to K^{-} K^{0} ν_τ$ in the extended NJL model with estimation of the contribution of the kaon final state interaction

The branching fraction of the decay $τ\to K^{-} K^{0} ν_τ$ is calculated in the framework of the extended Nambu--Jona-Lasinio model. The contact and vector channels are considered. The contributions to this process of the $ρ$ meson in the ground and first radially excited states are taken into account in the vector channel. The obtained results are in satisfactory agreement with the experimental data. Taking into account the kaon interaction in the final state results in insignificant corrections, which are not beyond the scope of the model uncertainties.

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arXiv2021

$1/N_c$ approximation and universality of vector mesons

In this work, we argue that the observed differences in the value of the vector coupling constant extracted from the decays $ρ\to ππ$ ($g_ρ = 6.0$), $ρ\to l^+l^-$ ($g_ρ = 5.0 $) and $ω\to l^+ l^-$ ($g_ρ = 5.7$), where $l=e,μ$, are an indication of the important role played by the $1/N_c$ corrections in the description of these processes. We show that an emission of a photon by charged meson loops in the $ρ^0, ω,ϕ\toγ$ transitions is a key process that allows to describe above vector meson decays into two leptons with a single value $g_ρ= 6.0$. Our result supports the idea of universality of neutral vector mesons and clarifies the role of accounting of $1/N_c$ corrections to its fulfilment.

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arXiv2021

The second-class current decays $τ\to πη(η') ν_τ$ in the NJL model including the interaction of mesons in the final state

The effect of the interaction of mesons in the final state is additionally considered within the description of $τ\to πη(η') ν_τ$ decays. This interaction is taken into account at the level of production of intermediate pions. One of them, in turn, might be transited into $η$ or $η'$ mesons. Our results do not exceed the experimentally established branching fractions, and they are in agreement with the results of other theoretical studies.

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arXiv2021

The decay $τ\to K^{-} ην_τ$ in the extended Nambu-Jona-Lasinio model taking into account the meson interaction in the final state

The branching fraction of the decay $τ\to K^{-} ην_τ$ has been calculated by using the extended Nambu-Jona-Lasinio model taking into account the meson interaction in the final state. The contact term and the channel with the intermediate ground $K^{*}(892)$ and first radially excited state $K^{*}(1410)$ have been calculated. For the purpose of describing the meson interaction in the final state, the triangle diagram with three mesons has been considered. The cutoff parameter of divergent integrals of the meson loop is equal to the appropriate parameter used in our previous work to describe the decay $τ\to K^{-} π^{0} ν_τ$. Thereby, the present work does not set any additional arbitrary parameters. The obtained results are in satisfactory agreement with the experimental data.

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arXiv2020

Fixing the vector coupling constant $g_ρ= 5.0$ in the NJL model and final-state interactions in processes $ρ\to e^+e^-[μ^+μ^-]$, $ρ\to π^+π^-$, $τ\to π^-π^0ν_τ$, and $e^+e^-\toπ^+π^-$

The possibility to use the width of the decay $ρ\to e^{+}e^{-}$ to fix the input parameter $g_ρ=5.0$ of the $SU(2) \times SU(2)$ chiral-symmetric Nambu--Jona-Lasinio model is discussed. It is shown that for a consistent simultaneous description of the processes $ρ\to e^{+}e^{-}$, $ρ\to π^{+}π^{-}$, $τ^{-} \to π^{-}π^{0} ν_τ$, and $e^{+}e^{-} \to π^{+}π^{-}$ can be constructed. Taking into account the interaction of pions in the final state appears to be important. The obtained theoretical results for the considered processes are in a satisfactory agreement with experimental data.

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arXiv2020

Processes $τ^- \to π^- π^0 ν_τ$ and $e^{+}e^{-} \to π^{+} π^{-}$ in the chiral NJL model with final state interactions taken into account

The processes $τ^- \to π^- π^0 ν_τ$ and $e^{+}e^{-} \to π^{+} π^{-}$ are considered within the chiral Nambu--Jona-Lasinio model with taking into account the pion final state interactions beyond the leading $1/N_c$ approximation. The contribution of the loop correction caused by a $ρ$ meson exchange between the pions, which gives the main contribution in the P-wave channel, is caclulated. The results for both processes are in a satisfactory agreement with experimental data.

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arXiv2020

On the mixing angle of the vector mesons $ω(782)$ and $ϕ(1020)$

In the present work, the mixing angle of the vector $ω(782)$ and $ϕ(1020)$ mesons is estimated in the framework of Nambu--Jona-Lasinio model. The decay $ϕ\to π^{0} γ$ is considered as a basic process to determine this angle. The obtained value is compared with the results of the other authors. Besides, the width of the decay $ϕ\to 3π$ and the cross-section of the process $e^{+}e^{-} \to π^{0} ϕ$ are calculated by using this angle.

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arXiv2020

Account for axial vector mesons in the $η\toπ^+π^-γ$ and $η' \toπ^+π^-γ$ decays

The rates and spectra of the anomalous $η\toπ^+π^-γ$ and $η' \toπ^+π^-γ$ decays are calculated. The approach is based on the effective meson Lagrangian obtained in the Nambu-Jona-Lasinio model with vector and axial-vector mesons by integrating out quark fields. The resulting action is affected by mixing between members of pseudoscalar $J^{PC}=0^{-+}$ and axial-vector $1^{++}$ nonets that violates some low-energy theorems. In this note we point out that a gauge covariant procedure to diagonalize this mixing allows for consistent description of the $η\toπ^+π^-γ$ and $η' \toπ^+π^-γ$ decays.

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arXiv2019

The decay $τ\to K^{*0}(892) K^- ν_τ$ in the extended NJL model

In the extended Nambu -- Jona-Lasinio model, the decay width of $τ\to K^{*0}(892) K^- ν_τ$ is calculated. The contributions from the contact diagram and diagrams with intermediate axial-vector, vector and pseudoscalar mesons in the ground and first radially excited states are taken into account. It is shown that axial-vector and vector channel with a contact diagram give a dominant contribution to the decay width. The obtained results for the decay width $τ\to K^{*0}(892) K^- ν_τ$ are in satisfactory agreement with experimental data. A prediction for differential distribution over the invariant mass of the meson pair $K^{*0}(892) K^-$ is given.

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arXiv2019

The decay $τ\to K^{*-}(892) ην_τ$ in the NJL model

The decay width $τ\to K^{*-}(892) ην_τ$ was calculated in the Nambu--Jona-Lasinio model. Four channels were taken into account: the contact channel (the final states are directly producted from lepton current without any intermediate meson states), the axial-vector channel with two intermediate physical states $K_{1}(1270)$ and $K_{1}(1400)$, the vector channel with intermediate $K^{*}(892)$ meson and the pseudoscalar channel with intermediate $K$ meson. It is shown that the first two channels give the dominant contribution to the decay width. Of the remaining two channels, the pseudoscalar channel plays a more prominent role. The final result is in satisfactory agreement with experimental data. Prediction for the differential decay width is presented.

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arXiv2019

The decays $τ\to [ω(782), ϕ(1020)] K^{-} ν_τ$ in the extended NJL model

In the extended Nambu--Jona-Lasinio model, the decay widths of the processes $τ\to [ω(782), ϕ(1020)] K^{-} ν_τ$ were calculated. The intermediate channels with axial vector ($K_{1}(1270)$, $K_{1}(1400)$ and $K_{1}(1650)$), vector ($K^{*}(892)$ and $K^{*}(1410)$) and pseudoscalar ($K$ and $K(1460)$) mesons were considered. The results for these processes are in satisfactory agreement with the experimental data.

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arXiv2019

The tetraquark $K_{1}(1400)$ in the decays $τ\to [ω(782), ϕ(1020)] K^{-} ν_τ$

In the extended Nambu--Jona-Lasinio model, the decay widths of the processes $τ\to [ω(782), ϕ(1020)] K^{-} ν_τ$ were calculated. The intermediate strange quark-antiquark mesons in both the ground and the first radially excited states were taken into account. The meson $K_{1}(1400)$, being a possible candidate for the role of the tetraquark meson, was also taken into account as an intermediate state. The result for the process $τ\to ω(782) K^{-} ν_τ$ is in satisfactory agreement with the experimental data. Simultaneously, the result for the decay $τ\to ϕ(1020) K^{-} ν_τ$ is in agreement with the experimental data with precision $1.3 σ$.

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arXiv2019

The decays $τ\rightarrow (K, K(1460))ν_τ$ and the value of the weak decay coefficients ${F}_{K}$ and ${{F}_{{K}^{'}}}$ in the extended NJL model

In the extended NJL model, the decay widths of $τ\rightarrow (K, K(1460))ν_τ$, $(K, K(1460))\rightarrow μν_μ$ are calculated. The contributions from intermediate axial-vector mesons ${K}_{1}(1270)$, ${K}_{1}(1400)$ and the first radially excited state ${K}_{1}(1650)$ are taken into account. Estimates for the weak decay coefficients ${F}_{K}$ and ${{F}_{{K}^{'}}}$ are given. Predictions are made for the width of $τ\rightarrow K(1460)ν_τ$ decay and ${{F}_{{K}^{'}}}$ constant.

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arXiv2018

Decay rates $f_{1}(1285)\to ρ^{0}π^{+} π^{-}$ and $a_{1}(1260)\toωπ^{+}π^{-}$ in the Nambu -- Jona-Lasinio model

The anomalous decays $f_1(1285)\toρ^0π^+π^-$ and $a_1(1260)\toωπ^+π^-$ violating natural parity for vectors and axial-vectors are studied in the framework of the Nambu -- Jona-Lasinio model. We consider the Lagrangian with $U(2)_L\times U(2)_R$ chiral symmetric four quark interactions. The theory is bosonized and corresponding effective meson vertices are obtained in the leading order of $1/N_c$ and derivative expansions. The uncertainties related with the surface terms of anomalous quark triangle diagrams are fixed by the corresponding symmetry requirements. We make a numerical estimate of the decay widths $Γ(f_1(1285)\toρ^0π^+π^-)=2.78\, \mbox{MeV}$ and $Γ(a_1(1260)\toωπ^+π^-)=87\, \mbox{keV}$. Our result on the $f_1(1285)\toρ^0π^+π^-$ decay rate is in a good agreement with experiment. It is shown that a strong suppression of the $a_1(1260)\toωππ$ decay is a direct consequence of destructive interference between box and triangle anomalies.

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arXiv2018

$τ\to f_1 (1285)π^{-} ν_τ$ decay in the extended Nambu -- Jona-Lasinio model

Within the framework of the extended Nambu -- Jona-Lasinio model, we calculate the matrix element of the $τ\to f_1(1285) π^{-} ν_τ$ decay, obtain the invariant mass distribution of the $f_1π$ -system and estimate the branching ratio Br$(τ\to f_1 π^{-}ν_τ)=4.0\times 10^{-4}$. The two types of contributions are considered: the contact interaction, and the axial-vector $I^G(J^{PC})=1^-(1^{++})$ resonance exchange. The latter includes the ground $a_1(1260)$ state, and its first radially excited state, $a_1(1640)$. The corrections caused by the $π-a_1$ transitions are taken into account. Our estimate is in a good agreement with the latest empirical result Br$(τ\to f_1 π^{-} ν_τ)=(3.9\pm 0.5)\times 10^{-4}$. The distribution function obtained for the decay $τ\to f_1(1285) π^{-} ν_τ$ shows a clear signal of $a_1(1640)$ resonance which should be compared with future experimental data including our estimate of the decay width $Γ(a_1(1640) \to f_1 π)=14.1\,\mbox{MeV}$.

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arXiv2018

Low energy process $e^{+}e^{-} \rightarrow K^{+} K^{-}$ in the extended Nambu-Jona-Lasinio model

In the extended Nambu-Jona-Lasinio model, the process of production of charged kaon pair on colliding electron-positron beams in the energy interval 1 - 1.7 GeV is described. In studying of this process, we take into account the contact terms when the pairs $K^{+}$ $K^{-}$ are generated by an intermediate photon, and processes with intermediate vector mesons $ρ$, $ω$ and $ϕ$ in the ground and in the first radially excited states. The results obtained here are compared with experimental data recently received in Novosibirsk and in Stanford.

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arXiv2018

The decay $τ\rightarrow f_1 πν_τ$ in the Nambu--Jona-Lasinio model

The width of the decay $τ\rightarrow f_1 πν_τ$ has recently been measured by the BaBar experiment. The estimation of this width is given in the framework of the NJL model with the axial-vector mesons. Prediction is in agreement with the experimental data. It is shown that the $π-a_1$ transition contribution plays an important role and allows us to bring the NJL prediction to the data.

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arXiv2018

Decays of $τ\rightarrow ρ(770) (ρ'(1450)) ν_τ$ and $τ\rightarrow K^{}(892) (K^{'}(1410)) ν_τ$ in the extended Nambu - Jona- Lasinio model

In the extended Nambu - Jona - Lasinio model the decay widths $τ\rightarrow ρ(770) (ρ'(1450)) ν_τ$ and $τ\rightarrow K^{*}(892) (K^{*'}(1410)) ν_τ$ are studied in the quark one -loop approximation. Our estimations of the decay widths $τ\rightarrow K^{*}(892) (K^{*'}(1410)) ν_τ$ are in satisfactory agreement with experimantal data. In the paper, the decay widths $τ\rightarrow ρ(770) (ρ'(1450)) ν_τ$ are also calculated.

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