Searcharxiv⌕ Search

arXiv subjects

Stanislav Dubnička

Publications and source records attributed to Stanislav Dubnička.

14 recordsLinked to original sources
arXiv2026

Zero of the proton electric form factor in the finite value of the spacelike momentum transfer squared

The behavior of the polarization data on $μ_p(G^p_E(t)/G^p_M(t))$ ratio, at the present day available up to $t=-8.5$ GeV$^2$, obtained in the Jefferson Lab experiments carried out by the Akhiezer-Rekalo polarization method, has a decreasing tendency, indicating possible existence of a zero of the proton electric form factor $G^p_E(t)$ in the finite spacelike momentum transfer squared value. However, recently appeared two papers, investigating these data, one of them including also other existing data on the nucleon electromagnetic structure in the spacelike and timelike regions, in which an existence of such zero is disproved. Nevertheless, reinvestigations we provide in this paper give clear arguments for the possible existence of such a zero.

hep-ph↗
arXiv2025

Selected decays of $B_{s}$ meson in covariant confined quark model

We present a study of various $B_{s}$ meson decays, including hadronic and semileptonic final states with different spins and diagram topologies. The covariant confined quark model is employed to describe hadronic effects, and our analysis serves as a broad test of the current understanding of the underlying dynamics within the Standard Model. The level of agreement with experimental data varies across channels: it is good for the semileptonic decays $B_{s}^{0}\to D_{s}^{-}μ^{+}ν_μ$ and $B_{s}^{0}\to K^{-}μ^{+}ν_μ$; acceptable for the hadronic modes $B_{s}^{0}\to D_{s}^{-}D^{+}$ and $B_{s}^{0}\to K^{-}π^{+}$; marginal for $B_{s}^{0}\to D_{s}^{-}π^{+}$, $B_{s}^{0}\to D_{s}^{-}ρ^{+}$, and $B_{s}^{0}\toϕ\,J/ψ$; and significantly discrepant for $B_{s}^{0}\toϕ\,\overline{D^{0}}$ and $B_{s}^{0}\toϕ\,η_{c}$. We argue that the observed inconsistencies may arise from the breakdown of naive factorization and unaccounted long-distance effects. In particular, the channels $B_{s}^{0}\to D_{s}^{-}π^{+}$ and $B_{s}^{0}\to D_{s}^{-}ρ^{+}$ are theoretically among the cleanest nonleptonic decays, yet they exhibit persistent discrepancies also reported by other theoretical groups.

hep-ph↗
arXiv2024

Analyzing leptonic decays of heavy quarkonia in covariant confined quark model

The leptonic decay widths of heavy quarkonia are complementary observables to the semileptonic decays of heavy mesons and provide additional insight into the possible lepton flavor universality breaking. We analyze the former in the framework of the covariant confined quark model, introducing a novel approach for the description of the radially excited quarkonia states, which is based on constituent quark mass running and the orthogonality of the states. We are able to describe the experimental observations by our approach within the Standard model, which does not support new physics explanations.

hep-ph↗
arXiv2023

B meson decays in covariant confined quark model

The aim of this text to present the covariant confined quark model (CCQM) and review its applications to the decays of $B$ mesons. We do so in the context of existing experimental measurements and theoretical results of other authors, which we review also. The physics principles are in detail exposed for the CCQM, the other results (theoretical and experimental) are surveyed in an enumerative way with comments. We proceed by considering successively three categories of decay processes: leptonic, semileptonic and non-leptonic.

hep-ph↗
arXiv2023

Study of damped oscillating structures from charged and neutral K-meson electromagnetic form factors data

The damped oscillating structures (OS) were recently revealed in the proton "effective" form factor (FF) data. For the time being they can be neither confirmed nor disproved by investigations of timelike data on the individual proton electric and proton magnetic FFs because their precision and reliability (especially of the proton electric FF data) has not achieved required level for this aim. On the other hand, conjectures that the OS are direct manifestations of the quark-gluon structure of the proton indicate that they must not be specific only for the proton and neutron, but that they should be present also for other hadrons. This opens a plausibility to find damped oscillatory structures also from the EM FFs data of such hadrons, for which adequate EM FFs data exist, by using the same procedure as for the proton. Consequently in this paper damped oscillatory structures are investigated in the EM FFs data of the charged and neutral $K$-mesons to be extracted from the corresponding production cross sections, $σ^{bare}_{tot}(e^+e^-\to K^+ K^-)$ measured from the threshold up to 64 GeV$^2$ and $σ^{bare}_{tot}(e^+e^-\to K_s K_L)$ measured from the threshold up to 9.5 GeV$^2$ of the total c.m. energy squared. The following results have been obtained. If the charged and neutral K-meson EM FFs timelike data are described by the three parametric formula by means of which OS have been revealed from the "effective" proton FF data then OS appear. If physically well founded Unitary and Analytic model of the K-meson EM structure is used for a description of the charged K-meson EM FFs data, no OS are visible. However, in the case of the neutral K-meson EM FF data one cannot make a definite decision. The overall results indicate that OS obtained from the "effective" proton FF data are likely an artefact of the three parametric formula which does not describe these data well.

hep-ph↗
arXiv2023

Search for damped oscillating structures from charged pion electromagnetic form factor data

The damped oscillating structures recently revealed by a three parametric formula from the proton ``effective'' form factor data extracted of the measured total cross section $σ^{bare}_{tot}(e^+e^-\to p\bar p)$ still seem to have an unknown origin. The conjectures of their direct manifestation of the quark-gluon structure of the proton indicate that they are not specific only of the proton and neutron, but they have to be one's own, similar to other hadrons. Therefore, the oscillatory structures from the charged pion electromagnetic form factor timelike data, extracted of the process $e^+e^-\to π^+ π^-$ are investigated by using the same procedure as in the case of the proton. The analysis shows the appearance of the oscillating structures in the description of the charged pion electromagnetic form factor timelike data by three parametric formula with a rather large value of $χ^2/ndf$, while the description of the data by the physically well-founded Unitary and Analytic model has not revealed any damped oscillating structures. From the obtained result on the most simple object of strong interactions, one can conclude that damped oscillating structures received from the ``effective'' proton form factor data are probably generated by a utilization of the improper three parametric formula which does not describe these data with sufficient precision.

hep-ph↗
arXiv2022

Decays $B\rightarrow D_{\left(s\right)}^{\left(*\right)}h$ ($h=π,ρ$) in confined covariant quark model

Decay processes $B\rightarrow D_{\left(s\right)}^{\left(*\right)}h$ ($h=π,ρ$) are studied in the framework of the confined covariant quark model using the naïve factorization assumption. We observe that the theoretical results on branching fractions have tendency to systematically exceed the experimental numbers. Such a behavior has already been seen for similar processes by other authors.

hep-ph↗
arXiv2021

Definite evidence for physically incomprehensible inequality $σ_{tot}(e^+e^- \to n \bar n) > σ_{tot}(e^+e^- \to p \bar p)$

Though the neutron mass is larger than the proton mass and obviously one expects in $e^+e^-$ annihilation a creation of more $p \bar p$ pairs in comparison with $n \bar n$ at the same energy, just the opposite inequality for the corresponding total cross sections $σ_{tot}(e^+e^- \to n \bar n) > σ_{tot}(e^+e^- \to p \bar p)$ has been revealed in the analysis of only the present time existing proton electromagnetic form factors data by the unitary and analytic approach.

hep-ph↗
arXiv2019

Study of $B_s\to\ell^+\ell^-γ$ decays in covariant quark model

We study the rare radiative leptonic decays $B_s\to\ell^+\ell^-γ$ ($\ell=e,μ,τ$) within the Standard Model, considering both the structure-dependent amplitude and bremsstrahlung. In the framework of the covariant confined quark model developed by us, we calculate the form factors characterizing the $B_s\toγ$ transition in the full kinematical region of the dilepton momentum squared and discuss their behavior. We provide the analytic formula for the differential decay distribution and give predictions for the branching fractions in both cases: with and without long-distance contributions. Finally, we compare our results with those obtained in other approaches.

hep-ph↗
arXiv2016

Decay $B_s\to ϕ\ell^+ \ell^-$ in covariant quark model

Our article is devoted to the study of the rare $B_s\to ϕ\ell^+\ell^-$ decay where $\ell=μ,τ$. We compute the relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The calculated form factors are used to evaluate branching fractions and polarization observables in the cascade decay $B\to ϕ(\to K^+K^-)\ell^+\ell^-$. We compare the obtained results with available experimental data and the results from other theoretical approaches.

hep-ph↗
arXiv2015

Decay $B\to K^\ast(\to Kπ) \ell^+ \ell^-$ in covariant quark model

Our article is devoted to the study of the rare $B\to K^\ast \ell^+\ell^-$~decay where $\ell=e,μ,τ$. We compute the relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The calculated form factors are used to evaluate branching fractions and polarization observables in the cascade decay $B\to K^\ast(\to Kπ)\ell^+\ell^-$. We compare the obtained results with available experimental data and the results from other theoretical approaches.

hep-ph↗
arXiv2013

Decays $B_{s}\rightarrow J/ψ+η$ and $B_{s}\rightarrow J/ψ+η'$ in the framework of covariant quark model

The covariant quark model represents an appropriate theoretical framework to describe the recent results on $B_{s}\rightarrow J/ψ+η$ and $B_{s}\rightarrow J/ψ+η'$ decays from the Belle collaboration. In this article we present the main features of he covariant quark model together with details on some of its aspects and methods, which we consider to be important. Further we apply the model specifically to the studied decay processes and give numerical results on decay widths as they follow from the odel. We conclude that the model, with most of its parameters previously fixed from different processes, is able to incorporate the new measurements from the Belle experiment.

hep-ph↗