By using the quark part of the energy-momentum tensor current, the gravitational formfactors of the $ ρ$ meson are calculated within the light-cone sum rules method. In the considered version, the energy-momentum tensor current is not conserved and as a result, there appear nine formfactors, six (three) of which correspond to the conservation (nonconservation) of the energy-momentum tensor current. We also compare our results with the one existing in the literature.
In present note the arguments in favour of future high statistical measurements of the formfactors that describe pi-meson decays into lepton-antilepton pair and photon are presented. It is shown that these formfactors Q^2 dependence contains the important information on the dynamics of quark motion inside a hadron.
We suggest a new scheme for the introduction of formfactors for the SU(4) chiral meson Lagrangian approach to the J/psi breakup cross sections by pion and rho meson impact. This mesonic formfactor scheme respects the fact that on the quark level of description the contact and the meson exchange diagrams are constructed by so-called box and triangle diagrams which contain a different number of vertex functions for the quark-meson coupling. We present a model calculation for Gaussian vertex functions within the meson formfactor scheme and compare the results with those of the usual global formfa…
We present a detailed analysis of the Bc form factors in the BSW framework, by investigating the effects of the flavor dependence on the average transverse quark momentum inside a meson. Branching ratios of two body decays of Bc meson to pseudoscalar and vector mesons are predicted.
The formfactors of B_1 -> pi and D_1 -> pi transitions, where B_1(D_1) is the 1^+ P-wave -> Q gamma_νγ_5q meson state, are calculated in the framework of the light cone QCD. Furthermore these formfactors are compared with the pole dominance model prediction using the values of the strong coupling constants g_{B_1 B^* pi} and g_{D_1 D^* pi}, and a good agreement between these two different descriptions is observed.
In framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare radiative kaon to pion and leptons $K^+ \to π^+ l^+ l^-$ and $K^0_S \to π^0 l^+ l^-$ and meson form factors. The comparison of these results with the present day experimental data shows us that the ChPT relations for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in the case of the neutral kaon decays $K^0 \to π^0 e^+ e^- (μ^+ μ^-)$ the formfactor data are known to a high precision than data on the differentia…
We study photon-meson transition formfactors of light mesons in the kinematics, where one photon is real and other is virtual. Dispersive approach to axial anomaly leads to the anomaly sum rule. The absence of corrections to it allows us to get the relation between possible corrections to continuum and to lower states within QCD method which does not rely on factorization hypothesis. We show, relying on the recent data of the BaBar Collaboration, that the relative correction to continuum is quite small, and small correction to continuum can dramatically change the pion formfactor. The same eff…
We use one-loop Heavy Meson Chiral Perturbation Theory (HMCHPT) as well as a relativistic formulation to calculate the chiral logarithms $m^2_π\log{\left(m^2_π/μ^2\right)}$ contributing to the formfactors of the semileptonic $B\rightarrow π$ decays at momentum transfer $q^2$ away from $q^2_\mathrm{max}=(m_B-m_π)^2$. We give arguments why this chiral behavior is reliable even in the energy regime with hard or fast pions. These results can be used to extrapolate the formfactors calculated on the lattice to lower light meson masses.
We present a QCD analysis of heavy quark mesons focussing on the B -> D* formfactor at zero recoil, F_D*(1). An advanced treatment of the perturbative corrections in the Wilsonian approach is presented. We estimate the higher-order power corrections to the OPE sum rule and describe a refined analysis of the nonresonant continuum contribution. In the framework of a model-independent approach, we show that the inelastic contribution in the phenomenological part of the OPE is related to the mQ-dependence of the hyperfine splitting and conclude that the former is large, lowering the prediction for…
We calculate the transition formfactors for the B -> K l(+) l(-) decay in the framework of the light cone QCD sum rules. The invariant dilepton mass distribution and the final lepton longitudinal polarization asymmetry are investigated. The comparison analysis of our results with traditional sum rules method predictions on the formfactors is performed.
The gravitational formfactor similar to shear viscosity is identified. In the time-like region it corresponds to the contribution of exotic hybrid meson. The exotic quantum numbers may be considered as a counterpart of dissipation in crossed channel. The ratio of viscosity to entropy density is estimated. The smallness due to holographic bound corresponds to the relative smallness of coupling of hybrid meson and the intrinsic transverse momentum, being the dynamical counterpart of temperature.
We investigate the transition formfactors for the B -> K^* l^+ l^- (l = mu, tau) decay in the light cone QCD. It is found that the light cone and 3-point QCD sum rules analyses for some of the formfactors for the decay B -> K^* l^+ l^- lead to absolutely different $q^2$ dependence. The invariant dilepton mass distributions for the B -> K^* mu^+ mu^- and B -> K^* tau^+ tau^- decays and final lepton longitudinal polarization asymmetry, which includes both short and long-distance contributions, are also calculated.
Dispersion relations allow for a coherent description of the nucleon electromagnetic form factors measured over a large range of momentum transfer, $Q^2 \simeq 0 \ldots 35$ GeV$^2$. Including constraints from unitarity and perturbative QCD, we present a novel parametrisation of the absorptive parts of the various isoscalar and isovector nucleon form factors. Using the current world data, we obtain results for the electromagnetic form factors, nucleon radii and meson couplings. We stress the importance of measurements at large momentum transfer to test the predictions of perturbative QCD.
We consider the QCD sum rules approach for Delta-isobar magnetic form factor in the infra-red region $0<Q^2<1GeV^2$. The QCD sum rules in external variable field are used. The obtained formfactor is in agreement with quark model predictions for the Delta-isobar magnetic moment.
Using the (modified) MIT bag model we calculated formfactors and decay widths for pseudoscalar - pseudoscalar and pseudoscalar - vector semileptonic decays of heavy to light mesons. We discuss the physical phenomena which are important in these processes and their influence on the measurable quantities. Our results are consistent with the available experimental data. A comparison with the results of other models is also given.
We investigate the semileptonic decays of B and D mesons into $π$ and $ρ$ mesons, respectively, by means of QCD sum rules. We find that for the vector formfactors involved the pole dominance hypothesis is valid to good accuracy with pole masses in the expected range. Pole dominance, however, does not apply to the axial formfactors which results in specific predictions for the predominant polarization of the $ρ$ meson and the shape of the lepton spectrum. For the total decay rates we find $Γ(\bar B^0 \to π^+ e^- \barν) = (5.1\pm 1.1)\,|V_{ub}|^2\, 10^{12}\,{\rm s^{-1}}$, $Γ( D^0 \to π^- e^+ ν) …
We summarize the results of the SU(4) chiral meson Lagrangian approach to the cross section for J/psi breakup by pion and rho meson impact and suggest a new scheme for the introduction of formfactors for the meson-meson interaction. This scheme respects the fact that on the quark level of description the contact and the meson exchange diagrams are constructed by so-called box and triangle diagrams which contain a different number of vertex functions for the quark-meson coupling. A model calculation for Gaussian vertex functions is presented and the relative importance of contact and meson exch…
We introduce and study the properties of the "color-straight" four-quark operators containing heavy and light quark fields. They are of the form (\bar bΓ_b b)(\bar qΓ_q q) where both brackets are color singlets. Their expectation values include the bulk of the nonfactorizable contributions to the nonleptonic decay widths of heavy hadrons. The expectation values of the color-straight operators in the heavy hadrons are related to the momentum integrals of the elastic light-quark formfactors of the respective heavy hadron. We calculate the asymptotic behavior of the light-current formfactors of h…
We discuss the production of soft photons in high energy hadron-hadron collisions. We present a model where quarks and antiquarks in the hadrons emit ``synchrotron light'' when being deflected by the chromomagnetic fields of the QCD vacuum, which we assume to have a nonperturbative structure. This gives a source of prompt soft photons with frequencies $ω<= 300 MeV$ in the c.m. system of the collision in addition to hadronic bremsstrahlung. In comparing the frequency spectrum and rate of ``synchrotron'' photons to experimental results we find some supporting evidence for their existence. We mak…
We report on recent progress on perturbative QCD calculations of certain exclusive rare weak $B$ meson decays involving hard photons. In the limit of a photon energy $E_γ$ much larger than $Λ_{QCD}$, the amplitudes for such processes can be analyzed in a twist expansion in powers of $Λ/E_γ$. The leading twist amplitude is given by the convolution of a hard scattering amplitude with the $B$ meson light-cone wavefunction. This approach is applied to a calculation of the leptonic radiative $B\to γ\ell ν_\ell$ formfactors and to an estimate of the weak annihilation contribution to the penguin deca…
I review the modern status of QCD theory of diffractive vector meson production with the focus on shrinkage of photons with Q2 and (Q2+mV2)$scaling, j-plane properties of the QCD pomeron and Regge shrinkage of diffraction cone, $s$-channel helicity non-conservation and sensitivity to spin-orbital properties of vector mesons.
We show that AdS/QCD generates predictions for the rate of diffractive rho meson electroproduction that are in agreement with data collected at the HERA electron-proton collider.
I review recent progress on understanding QCD dynamics involved in exclusive $B$ meson decays. Different frameworks, including light-cone sum rules, QCD factorization, perturbative QCD, soft-collinear effective theory, light-front QCD, are discussed. Results from lattice QCD are quoted for comparison. I point out the important issues in the above QCD methods, which require further investigation.
The meson spectroscopy is studied in the framework of the QCD string model. The mesons are composed of spinless quarks which move relativistically. We show that the QCD string model reproduces the straight line Regge trajectories and exibit the correct string slopes for both light-light and heavy-light mesons. We also present the exact numerical solution and the analytic approximation solution of the QCD string equations for the light-light mesons under the deep radial limit. We demonstrate that the QCD string model describes the universal relations for the light-light and heavy-light meson sp…
We estimate the strong coupling constants of charmed and bottom mesons $ D_{(s)}^* $, $ D_{(s)1} $, $ B_{(s)}^* $, and $ B_{(s)1} $ with light vector mesons $ ρ$, $ ω$, $ K^* $, and $ ϕ$ within the framework of light-cone QCD sum rules. We compare our estimations to the ones predicted by other approaches.
We present a systematic study of twist-4 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. The structure of meson mass corrections is studied in detail. A complete set of distribution amplitudes is constructed, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules. Our study suggests that meson mass corrections may present a dominant source of higher twist effects in exclusive processes.
Decay constant of eta-meson f is calculated on the basis of the QCD sum rule method. An instanton contribution is taken into account. The result is f = 0.17 GeV.
Within the framework of non-local quark model of Nambu--Jona-Lasinio type the two-photon decay of radial excited state of $π_0$-meson -- $π_0'$ -- is found to be $3.6\KeV$. The radial excitation of pion is described with the use of polynomial formfactor of second order over $\vec q^2$ where $\vec q$ is the transverse momentum, which corresponds to relative motion of quark-antiquark pair within the energy range from 0 up to $1\GeV$. The probabilities of production of $π_0'$ and $(π_0'+γ)$ states in the electron-positron colliders are estimated. The production of $π_0'$-meson in the interaction …
The magnetic and quadrupole moments of the light-vector and axial-vector mesons are calculated in the light cone QCD sum rules. Our results for the static properties of these mesons are compared with the predictions of lattice QCD as well as other approaches existing in the literature.
The electromagnetic form factor of the eta meson is studied using the Light Cone QCD sum rules approach taking in to account higher twists contributions and SU(3) flavor symmetry breaking effects.
The bilocal effective action is developed as a viable tool to study mesons in the large-N limit of QCD. Several results from current algebra are derived in a new way using this action. The question of gauge invariance is discussed in an appendix
In this manuscript, a unified approach to hadron physics from holographic point of view is described. After introduction of a general setup for meson-nucleon system based on the bottom-up approach of QCD (AdS/QCD), as an illustration, we specifically examine meson-nucleon couplings. This is an example of the notion we call "holographic unification" in hadron physics.
Magnetic dipole moments of the negative parity light and heavy tensor mesons are calculated within the light cone QCD sum rules method. The results are compared with the positive parity counterparts of the corresponding tensor mesons. The results of the analysis show that the magnetic dipole moments of the negative parity light mesons are smaller compared to those of the positive parity mesons. Contrary to the light meson case, magnetic dipole moments of the negative parity heavy mesons are larger than the ones for the positive parity mesons.
Experimental results from HERA on diffractive vector meson production and their theoretical interpretation within microscopic QCD are reviewed with an emphasis on the BFKL color dipole and kt-factorization approaches.
The B-meson distribution amplitude is calculated using QCD sum rules. In particular we obtain an estimate for the integral relevant to exclusive B-decays λ_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated parametrization of the distribution amplitude is suggested.
We consider the light-front holographic QCD with the light-front wave functions for mesons, modified for massive quarks. We evaluate the wave functions, distribution amplitudes, and form factors for $π$, $ρ$, $K$, and $J/ψ$ mesons and photon-to-meson transition form factors for $π$, $η$, and $η^\prime$ mesons. The results are compared with the experimental data, wherever available.
Recently, LHCb Collaboration announced the discovery of radial excitations of $D_s$ and $B_s$ mesons. In present work, we calculate the most promising strong and electromagnetic decay widths of radially excited $D_s(2S)$ and $B_s(2S)$ mesons within the light cone QCD sum rules method.
The magnetic moment $μ$ of the "rho" meson is studied in QCD light cone sum rules, and it is found that "mu = (2.3 pm 0.5)". A comparison of our result on the magnetic moment of the "rho" meson with the predictions of the other approaches, is presented.
We focus on the chiral and heavy quark mass expansion of mesons masses and decay constants. We propose a light-front QCD formalism for the evaluation of these quantities, consistent with chiral perturbation theory and heavy quark effective theory.
An update is given of the determination of leptonic decay constants of charm and beauty mesons in the framework of relativistic Hilbert moments and Laplace transform QCD sum rules.
The light-front wavefunction for mesons predicted by holographic light-front QCD is used to obtain the light-cone distribution amplitudes for the light vector mesons and the transition form factors for B and $B_s$ decays to $ρ$, $K^*$ and $ϕ$ mesons. Here, I present some of our predictions as compared to lattice QCD, OCD sum rules and the available experimental data.
We present a systematic study of twist-4 light-cone distribution amplitudes of the $K^*$ and $ϕ$ meson in QCD. The structure of SU(3)-breaking corrections is studied in detail. Non-perturbative input parameters are estimated from QCD sum rules and a renormalon based model. As a by-product, we give a complete reanalysis of the parameters of the twist-4 $ρ$-meson distribution amplitudes.
We present predictions for rho-meson form factors obtained from the analysis of QCD sum rules in next-to-leading order of perturbation theory. The radiative corrections turn out to be sizeable and should be taken into account in rigorous theoretical analysis.
We study light scalar mesons in the AdS/QCD soft-wall model with a background dilaton field. The masses and decay constants are compatible with experiment and QCD determinations if $a_0(980)$ and $f_0(980)$ are identified as the lightest scalar mesons; moreover, the states are organized in linear Regge trajectories with the same slope of vector mesons. Comparing the two-point correlation function of scalar operators in AdS and QCD, information about the condensates can be derived. Strong couplings of scalar states to pairs of light pseudoscalar mesons turn out to be small, at odds with experim…
The rho-meson magnetic moment is calculated in the framework of QCD sum rules in external fields. Bare loop calculations (parton model) give 2.0. The contribution of the operators of dimension 6 reduces this value to 1.5.
We investigate the finite-temperature spectral functions of heavy quarkonia by using the soft-wall AdS/QCD model. We discuss the scalar, the pseudo-scalar, the vector, and the axial-vector mesons and compare their qualitative features of the melting temperature and growing width. We find that the axial-vector meson melts earlier than the vector meson, while there appears only a slight difference between the scalar and pseudo-scalar mesons which also melt earlier than the vector meson.
A simple matching procedure is proposed to extract constraints on effective meson theories. In this way, a QCD prediction for the pion decay constant is found, F(pi)=2 m(pi)/pi, i.e. approximately 90MeV. The same procedure also determines other mesonic observables, like the decay width of the sigma meson to two photons. Finally, some information which can be gained about the hadronic light-by-light contributions to the muon anomalous moment are briefly commented.
In the present work, the temperature dependence of the scalar mesons parameters is investigated in the framework of thermal QCD sum rules. We calculate sigma-pole and the non-resonant two-pion continuum contributions to the spectral density. Taking into account additional operators appearing at finite temperature, the thermal QCD sum rules are derived. The temperature dependence of the shifts in the mass and leptonic decay constant of scalar sigma(600) meson is calculated.
The magnetic and quadrupole moments of the vector and axial-vector mesons containing heavy quark are estimated within the light cone sum rules method. Our predictions on magnetic moments for the vector mesons are compared with the results obtained by other approaches.
The mass radius is a fundamental property of the proton that so far has not been determined from experiment. Here we show that the mass radius of the proton can be rigorously defined through the formfactor of the trace of the energy-momentum tensor (EMT) of QCD in the weak gravitational field approximation, as appropriate for this problem. We then demonstrate that the scale anomaly of QCD enables the extraction of the formfactor of the trace of the EMT from the data on threshold photoproduction of $J/ψ$ and $Υ$ quarkonia, and use the recent GlueX Collaboration data to extract the r.m.s. mass r…
We study light scalar mesons in the AdS/QCD soft-wall model with a background dilaton field, to investigate the features of this approach in describing QCD properties in the strong coupling regime. We find that the masses and decay constants are compatible with experiment and QCD determinations if $a_0(980)$ and $f_0(980)$ are identified as the lightest scalar mesons; moreover, the states are organized in linear Regge trajectories with the same slope of vector mesons. Strong couplings of scalar states to pairs of light pseudoscalar mesons turn out to be small, at odds with experiment and QCD e…
Wave functions and energy eigenvalues of the path integral Hamiltonian are studied in Lorentz frame moving with velocity $v$. The instantaneous interaction produced by the Wilson loop is shown to be reduced by an overall factor $\sqrt{1-(\frac{v}{c})^2}$. As a result one obtains the boosted energy eigenvalues in the Lorentz covariant form $E= \sqrt{\veP^2+M^2_0}$, where $M_0$ is the c.m. energy, and this form is tested for two free particles and for the Coulomb and linear interaction.Using Lorentz contracted wave functions of the bound states one obtains the scaled parton wave functions and va…
The leading-twist distribution amplitude for the longitudinal rho-meson was studied using QCD Sum Rules with nonlocal condensates and a spectral density which includes next-to-leading order radiative corrections. The obtained profile is compared with results from standard QCD sum rules, lattice QCD, holographic QCD, a light-front quark model, and the instanton liquid model. Preliminary estimates for the first two moments of the transverse $ρ$-meson distribute amplitude are also given.
Semileptonic decays of D-mesons into scalar hadronic states are investigated. Two extreme cases are considered: a) the meson decays directly into an uncorrelated scalar state of two two mesons and b) the decay proceeds via resonance formation. QCD sum rules including instanton contributions are used to calculate total and differential decay rates under the two assumptions.
