arXiv subjects

M. A. Ivanov

Publications and source records attributed to M. A. Ivanov.

At least 19 recordsLinked to original sources

arXiv2024

Hidden-charm strong decays of the spin-$2$ partner of $X(3872)$

Hidden-charm strong decays of the spin-2 partner $X_2(4014)$ of the charmonium-like state $X(3872)$ have been studied in the framework of the covariant confined quark model. The exotic state $X_2$ has been interpreted as a four-quark state with molecular-type interpolating current. We have considered the decay widths of $X_2$ on the level of two-petal quark loops. The partial widths of the strong decays $X_2\!\to\!ω\, J/Ψ$ and $X_2\!\to\!ρ^0 \, J/Ψ$ have been calculated and the related branching ratio has been analyzed.

hep-ph↗

arXiv2023

Strong decays of charmonium-like state Y(4230)

Strong decays of the charmonium-like state $Y(4320)$ have been studied in the framework of the covariant confined quark model. The resonance $Y$ has been interpreted as a four-quark state of the molecular type. We evaluate the hidden-charm decay width of $Y$ to a vector and a scalar, with the latter decaying subsequently to a pair of charged pseudoscalar states. The strong decay modes $Y \!\to\! π^{+}π^{-}J/Ψ$ and $Y \!\to\! K^{+}K^{-} J/Ψ$ have been studied by involving the scalar resonance state $f_0(980)$. We have calculated the fractal widths of the related strong decays and the branching ratio ${\cal B}(Y \!\to\! K^{+}K^{-} J/Ψ)$ / ${\cal B}(Y \!\to\! π^{+}π^{-}J/Ψ)$, recently determined by the BESIII collaboration. The estimated branching ratio and calculated fractal strong decay widths are in good agreement with the latest experimental data, favoring the molecular representation of the $Y(4320)$ state.

hep-ph↗

arXiv2016

Wave formation process upon explosive welding: electron microscopic observations and imitating experiments

A sequence of the interface transition states was investigated. A transition state has been found, during which cusps look like splashes. Images of the splashes for different joints have been obtained. The processes of self-organization of the splashes into a quasi-wave surface and a perfect wavy surface have been revealed. Simulations experiments have been conducted. Heterogeneity and the interface bending of one of the contacting materials have been detected. They imitate the heterogeneity on the interface arising upon explosive welding.

physics.ins-det↗

arXiv2009

Flavourful hadronic physics

We review theoretical approaches to form factors that arise in heavy-meson decays and are hadronic expressions of non-perturbative QCD. After motivating their origin in QCD factorisation, we retrace their evolution from quark-model calculations to non-perturbative QCD techniques with an emphasis on formulations of truncated heavy-light amplitudes based upon Dyson-Schwinger equations. We compare model predictions exemplarily for the B\toπtransition form factor and discuss new results for the g_{D*Dπ} coupling in the hadronic D* decay.

nucl-th↗

arXiv2009

Complete structure dependent analysis of the decay $P \to l^{+}l^{-}$

We use the Mellin-Barnes representation in order to improve the theoretical estimate of mass corrections to the width of light pseudoscalar meson decays into a lepton pair, $P\to l^{+}l^{-}$ . The full resummation of the terms $(M^{2}/Λ^{2}) ^{n},$ $(m^{2}/M^{2}) ^{n}$and $(m^{2}/Λ^{2}) ^{n}$ to the decay amplitude is performed, where $m$ is the lepton mass, $M$ is the meson mass and $Λ\approx m_ρ$ is the characteristic scale of the $P\to γ^{\ast}γ^{\ast}$ form factor. The total effect of mass corrections is quite important for $η(η^{\prime})$ decays. We also comment on the estimation of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment in the chiral perturbation theory.

hep-ph↗

arXiv2008

On mass corrections to the decays P \to l^+l^-

We use the Mellin-Barnes representation in order to improve the theoretical estimate of mass corrections to the width of light pseudoscalar meson decay into a lepton pair, $P\to l^+l^-$ . The full resummation of the terms $\ln(m_l^2/Λ^2)(m_l^2/Λ^2)^n$ and $(m_l^2/Λ^2)^n$ to the decay amplitude is performed, where $m_l$ is the lepton mass and $Λ\approx m_ρ$ is the characteristic scale of the $P\toγ^*γ^*$ form factor. The total effect of mass corrections for the $e^+e^-$ channel is negligible and for the $μ^+μ^-$ channel its order is of a few per cent.

hep-ph↗

arXiv2006

Magnetic moments of heavy baryons in the relativistic three-quark model

The magnetic moments of ground state single, double and triple heavy baryons containing charm or bottom quarks are calculated in a relativistic three-quark model, which, in the heavy quark limit, is consistent with Heavy Quark Effective Theory and Heavy Hadron Chiral Perturbation Theory. The internal quark structure of baryons is modeled by baryonic three-quark currents with a spin-flavor structure patterned according to standard covariant baryonic wave functions and currents used in QCD sum rule calculations.

hep-ph↗

arXiv2005

The exclusive rare decays B -> K l(bar) l and B_c -> D(D*) l(bar) l in a relativistic quark model

We study the exclusive rare decay B -> K l(bar) l. We calculate the relevant form factors within a relativistic constituent quark model, for the first time without employing the impulse approximation. The calculated form factors are used to evaluate differential decay rates and polarization observables. We present results on the q2-dependence of a set of observables with and without long-distance contributions. A similar analysis is done for the exclusive rare decays B_c -> D (D*) l(bar) l with special emphasis on the cascade decay B_c -> D* (-> D pi) l(bar) l. We derive a four-fold angular decay distribution for this process in terms of helicity amplitudes including lepton mass effects. The four-fold angular decay distribution allows to define a number of physical observables which are amenable to measurement. We compare our results with the results of other studies.

hep-ph↗

arXiv2003

Pion and sigma meson properties in a relativistic quark model

A variety of strong and electroweak interaction properties of the pion and the light scalar sigma meson are computed in a relativistic quark model. Under the assumption that the resulting coupling of these mesons to the constituent quarks is identical, the sigma meson mass is determined as M_sigma=385.4 MeV. We discuss in detail the gauging of the non-local meson-quark interaction and calculate the electromagnetic form factor of the pion and the form factors of the pi(0) -> gamma gamma and sigma -> gamma gamma processes. We obtain explicit expressions for the relevant form factors and evaluate the leading and next-to-leading orders for large Euclidean photon virtualities. Turning to the decay properties of the sigma we determine the width of the electromagnetic sigma -> gamma gamma transition and discuss the strong decay sigma -> pi pi. In a final step we compute the nonleptonic decays D -> sigma pi and B -> sigma pi relevant for the possible observation of the sigma meson. All our results are compared to available experimental data and to results of other theoretical studies.

hep-ph↗

arXiv2003

The nonleptonic decays Bc->Ds antiD0 and Bc->Ds D0 in a relativistic quark model

In the wake of exploring CP-violation in the decays of B and Bc mesons, we perform the straightforward calculation of their nonleptonic decay rates within a relativistic quark model. We confirm that the decays Bc->Ds antiD0 and Bc->Ds D0 are well suited to extract the Cabibbo-Kobayashi-Maskawa angle γthrough the amplitude relations because their decay widths are the same order of magnitude. In the b-c sector the decays B->D K and Bc->DD lead to squashed triangles which are therefore not so useful to determine the angle experimentally. We also determine the rates for other nonleptonic Bc-decays and compare our results with the results of other studies.

hep-ph↗

arXiv2002

Heavy Quarks on the Lattice

I review the basic ideas behind lattice QCD calculations that involve charm and bottom quarks. I report on the progress in getting the correct hyperfine splitting in charmonium from lattice QCD. Some of the basic technology behind numerical lattice QCD calculations is explained by studying some specific examples: computation of the charm quark mass, and the calculation of fB.

hep-lat↗

arXiv2002

Ground-state energy of pionic hydrogen to one loop

We investigate the ground-state energy of the pi- p atom (pionic hydrogen) in the framework of QCD+QED. In particular, we evaluate the strong energy-level shift. We perform the calculation at next-to-leading order in the low-energy expansion in the framework of the relevant effective field theory. The result provides a relation between the strong energy shift and the pion-nucleon S-wave scattering lengths - evaluated in pure QCD - at next-to-leading order in isospin breaking and in the low-energy expansion. We compare our result with available model calculations.

hep-ph↗

arXiv2001

Semileptonic decays of double heavy baryons

We study the semileptonic decays of the lowest lying double heavy baryons using the relativistic three-quark model. We do not employ a heavy quark mass expansion but keep the masses of the heavy quarks and baryons finite. We calculate all relevant form factors and decay rates.

hep-ph↗

arXiv2000

The semileptonic decays of the B_c meson

We study the semileptonic transitions B_c to η_c, J/ψ, D, D^*, B, B^*, B_s, B_s^* in the framework of a relativistic constituent quark model. We use experimental data on leptonic J/ψdecay, lattice and QCD sum rule results on leptonic B_c decay, and on radiative η_c transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic B_c-transitions and give predictions for various semileptonic B_c decay modes including their τ-modes when they are kinematically accessible. The implications of heavy quark symmetry for the semileptonic decays are discussed and are shown to be manifest in our explicit relativistic quark model calculation. A comparison of our results with the results of other calculations is performed.

hep-ph↗

arXiv2000

Heavy-Meson Observables via Dyson-Schwinger Equations

We summarise a Dyson-Schwinger-equation-based calculation of an extensive range of light- and heavy-meson observables, characterised by heavy-meson leptonic decays, semileptonic heavy-to-heavy and heavy-to-light transitions, radiative and strong decays, and the rare flavour-changing neutral-current process. In the calculation the heavy-quark mass functions are approximated by constants, interpreted as their constituent mass.

hep-ph↗

arXiv2000

Dyson-Schwinger Equation Approach to the QCD Deconfinement Transition and J/Psi Dissociation

We consider an extension of the finite-temperature Dyson-Schwinger equation (DSE) approach to heavy mesons and quarkonia and apply it to calculate the cross section for the J/Psi breakup reaction J/Psi + pi --> D + D. We study the effects of chiral symmetry restoration in the light quark sector on this process and obtain a critical enhancement of the reaction rate at the chiral/ deconfinement transition. Implications for the kinetics of charmonium production in ultrarelativistic heavy-ion collisions are discussed with particular emphasis on the recently observed anomalous J/Psi suppression as a possible signal for quark matter formation.

hep-ph↗

arXiv1999

On the choice of heavy baryon currents in the relativistic three-quark model

We test the sensitivity of bottom baryon observables with regard to the choice of the interpolating three-quark currents within the relativistic three-quark model. We have found that the semileptonic decay rates are clearly affected by the choice of currents, whereas the asymmetry parameters show only a very weak dependence on the choice of current.

hep-ph↗

arXiv1999

Decay Constants and Semileptonic Form Factors of Pseudoscalar Mesons

A relativistic constituent quark model is adopted to give an unified description of the leptonic and semileptonic decays of pseudoscalar mesons (π, K, D, D_s, B, B_s). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and the results of other approaches. Eventually, the model is found to reproduce the scaling behaviours of spin-flavor symmetry in the heavy-quark limit.

hep-ph↗