arXiv subjects
Publications and source records attributed to Valery E. Lyubovitskij.
We derive a light-front Schrodinger-type equation of motion for the quark-antiquark wave function of heavy quarkonia imposing constraints from the holographic soft-wall model.
The annihilation process p bar(p) -> p D0 bar(Lambda)_c(2286) is studied taking into account t-channel D0, D*0 meson exchange and the resonance contribution of Lambda_c(2286) and Lambda_c(2940) baryons. We assume that the Lambda_c(2940) baryon is a pD*0 molecular state with spin-parity (1/2)+ and (1/2)-. Our results show that near the threshold of p bar(p) -> Lambda_c(2286) bar(Lambda)_c(2286) the contribution from the intermediate state Lambda_c(2940) is also sizeable and can be observed at the PANDA experiment. Another conclusion is that the spin-parity assignment (1/2)- for Lambda_c(2940) gives enhancement for the cross section in comparison with a choice (1/2)+.
The newly observed hidden-charm meson Zc(3900) with quantum numbers J(P) = 1(+) is considered as a hadronic molecule composed of DD*. We give detailed predictions for the decay modes Zc(+) -> J/psi + pi(+) + gamma and Zc(+) -> J/psi + pi(+) + l(+) + l(-) (l = e, mu) in a phenomenological Lagrangian approach.
We apply a phenomenological Lagrangian approach to the radiative decay Y(4260) -> X(3872) + gamma. The Y(4260) and X(3872) resonances are considered as composite states containing both molecular hadronic and charmonium components. Having a leading molecular component in the X(3872) and a sole molecular configuration for the Y(4260) results in a prediction compatible with present data.
We present a detailed analysis of the heavy-to-light semileptonic decays of the Lambda_b and Lambda_c baryons Lambda_b -> p l- bar(nu)_l and Lambda_c -> n l+ nu_l in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters.
We provide a new insight into the problem of generating the hadron mass spectrum in the framework of the covariant confined quark model. One of the underlying principles of this model is the compositeness condition which means that the wave function renormalization constant of the elementary hadron is equal to zero. In particular, this equation allows to express the Yukawa coupling of the meson fields to the constituent quarks as a function of other model parameters. In addition to the compositeness condition we also employ a further equation which relates the meson mass function to the Fermi coupling. Both equations guarantee that the Yukawa-type theory is equivalent to the Fermi-type theory thereby providing an interpretation of the meson field as the bound state of its constituent fermions (quarks). We evaluate the Fermi-coupling as a function of meson (pseudoscalar and vector) masses and vary the values of the masses in such a way to obtain a smooth behavior for the resulting curve. The mass spectrum obtained in this manner is found to be in good agreement with the experimental data. We also compare the behavior of our Fermi-coupling with the strong QCD coupling alpha_s calculated in an QCD-inspired approach.
In present work the Y(4260) resonance is considered as a weakly bound state of a pseudoscalar D and an axial D1 charm meson. We consider the two-body decay Y(4260) -> Zc(3900) + pi where Zc(3900) is treated as hadron molecule as well. Moreover we compute the Y(4260) decay modes J/psi pi(+) pi(-), recently observed by the BESIII Collaboration, and psi(2S) pi(+) pi(-). In the last process both the contact diagram with D D1 -> psi(nS) pi(+) pi(-) and the resonance diagram with D D1 -> Zc(3900) + pi -> psi(nS) pi(+) pi(-) are taken into account.
A relativistic light-front quark model is used to describe both the elastic nucleon and nucleon-Roper transition form factors in a large Q2 range, up to 35 GeV2 for the elastic and up to 12 GeV2 for the resonance case. Relativistic three-quark configurations satisfying the Pauli exclusion principle on the light-front are used for the derivation of the current matrix elements. The Roper resonance is considered as a mixed state of a three-quark core configuration and a molecular N+sigma hadron component. Based on this ansatz we obtain a realistic description of both processes, elastic and inelastic, and show that existing experimental data are indicative of a composite structure of the Roper resonance.
Peculiarities of obtaining parameters for broad multi-channel resonances from data are discussed analyzing the experimental data on processes $ππ\toππ,K\bar{K}$ in the $I^GJ^{PC}=0^+0^{++}$ channel in a model-independent approach based on analyticity and unitarity and using an uniformization procedure. We show that it is possible to obtain a good description of the $ππ$ scattering data from the threshold to 1.89 GeV with parameters of resonances cited in the PDG tables as preferred. However, in this case, first, representation of the $ππ$ background is unsatisfactory; second, the data on the coupled process $ππ\to K\bar{K}$ are not well described even qualitatively above 1.15 GeV when using the resonance parameters from the only $ππ$ scattering analysis. The combined analysis of these coupled processes is needed, which is carried out satisfactorily. Then both above-indicated flaws, related to the analysis of solely the $ππ$-scattering, are cured. The most remarkable change of parameters with respect to the values of only $ππ$ scattering analysis appears for the mass of the $f_0 (600)$ which is now in some accordance with the Weinberg prediction on the basis of mended symmetry and with an analysis using the large-$N_c$ consistency conditions between the unitarization and resonance saturation. The obtained $ππ$-scattering length $a_0^0$ in case when we restrict to the analysis of the $ππ$ scattering or consider so-called A-solution (with a lower mass and width of $f_0(600)$ meson) agrees well with prediction of chiral perturbation theory (ChPT) and with data extracted at CERN by the NA48/2 Collaboration from the analysis of the $K_{e4}$ decay and by the DIRAC Collaboration from the measurement of the $π^+π^-$ lifetime.
The $f_0$ mesons are studied in a combined analysis of data on the isoscalar S-wave processes $ππ\toππ,K\overline{K},ηη$ and on decays $J/ψ\toϕ(ππ, K\overline{K})$, $ψ(2S)\to J/ψ(ππ)$, and $Υ(2S)\toΥ(1S)ππ$ from the Argus, Crystal Ball, CLEO, CUSB, DM2, Mark II, Mark III, and BES II collaborations. The method of analysis, based on analyticity and unitarity and using an uniformization procedure, is set forth with some details. Some spectroscopic implications from results of the analysis are discussed.
We calculate the invariant and helicity amplitudes for the nonleptonic decay Lambda_b -> Lambda + J/psi, psi(2S) in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay Lambda_b -> Lambda(-> p pi-) + J/psi, psi(2S) (-> l+ l-) and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from the naive quark model that the transitions into the lambda_Lambda=1/2 helicity states of the daughter baryon Lambda are strongly suppressed leading to a near maximal negative polarization of the Lambda. For the same reason the azimuthal correlation between the two decay planes spanned by (p pi-) and (l+ l-) is negligibly small. We provide form factor results for the whole accessible q2-range. Our results are close to lattice results at minimum recoil and light-cone sum rule results at maximum recoil. A new feature of our analysis is that we include lepton mass effects in the calculation which allows us to also describe the cascade decay Lambda_b -> Lambda(-> p pi-) + psi(2S)(-> tau+ tau-).
The two newly observed hidden-charm mesons Zc(+)[3900] and a possible partner state Zc'(+)[3950] with quantum numbers J(P) = 1(+) are considered as hadronic molecules composed of bar(D)D* and bar(D)* D*, respectively. We give predictions for the decay widths of the strong two-body transitions Zc(+) -> H + pi(+) and Zc' -> H + pi(+) with H = Psi(nS), hc(mP) in a phenomenological Lagrangian approach.
We study the helicity-independent generalized parton distributions of nucleons in the zero skewness case, based on a particular light-front quark model derived in a soft-wall AdS/QCD approach.
We propose a phenomenological light-front wave function for hadrons with arbitrary twist-dimension (mesons, baryons and multiquark states), which gives the correct scaling behavior of structure functions (parton distributions) and form factors for pions and nucleons. For other hadronic states the proposed wave function produces form factors consistent with quark counting rules, and gives predictions for structure functions (parton distributions). As an application we build a light-front quark model for nucleons based on the proposed wave function.
Using the covariant constituent quark model previously developed by us we calculate the differential rate and the forward-backward asymmetries on the lepton and hadron side for the rare baryon decays Lambda_b -> Lambda l+ l- (l=e, mu, tau) and Lambda_b -> Lambda gamma. We use helicity methods to write down a three-fold joint angular decay distribution for the cascade decay Lambda_b -> Lambda (-> p pi-) + J_eff (-> l+ l-). Through appropriate angular integrations we obtain expressions for the rates, the lepton-side forward-backward (FB) asymmetry and the polarization of the daughter baryon Lambda leading to a hadron-side forward-backward asymmetry. We present numerical results on these observables using the covariant quark model and compare our results to the results of other calculations that have appeared in the literature.
We revisit the status of Lepton Flavor Violating (LFV) μe qq contact interactions from the view point of μ- e -conversion in nuclei. We consider their contribution to this LFV process via the two mechanisms on the hadronic level: direct nucleon and meson exchange ones. In the former case the quarks are embedded directly into the nucleons while in the latter in mesons which then interact with nucleons in a nucleus. We revise and in some cases reevaluate the hadronic parameters relevant for both mechanisms and calculate the contribution of the above mentioned contact interactions in coherent μ- e -conversion in various nuclei. Then we update the existing upper bounds and also derive new ones for the scales of the μe qq contact interactions from the experimental limits on the capture rates of μ- e -conversion. We compare these limits with the ones derived in the literature from other LFV processes and comment on the prospects of LHC searches related to the contact μe qq interactions.
We describe the electroproduction of the N(1440) Roper resonance in soft-wall AdS/QCD. The Roper resonance is identified as the first radially excited state of the nucleon, where higher-Fock states in addition to the three-quark component are included. The main conclusion is that the leading 3q component plays the dominant role in the description of electroproduction properties of this resonance: form factors, helicity amplitudes and charge densities. The obtained results are in good agreement with the recent results of the CLAS Collaboration at JLab.
We consider mesons composed of light and heavy quarks and discuss the construction of the corresponding meson wave functions in soft-wall AdS/QCD. We specifically take care that constraints imposed by chiral symmetry breaking and by the heavy quark limit are fulfilled. The main results are: i) the wave functions of light mesons have a nontrivial dependence on the current quark mass, which gives rise to a mass spectrum consistent with the one including explicit breaking of chiral symmetry; ii) the wave functions of heavy-light mesons generate their correct mass spectrum, the mass splittings of vector and pseudoscalar states, and the correct scaling of leptonic decay constants f(Q \bar q) \sim 1/sqrt(mQ); iii) the wave functions of heavy quarkonia produce their correct mass spectrum and lead to a scaling behaviour of the leptonic decay constants f(Q \bar Q) \sim sqrt(mQ) and f(c \bar b) \sim mc/sqrt(mb) at mc << mb, consistent with potential models and QCD sum rules.