Using a counting scheme which treats pseudoscalar and vector mesons on equal footing, the decays of the narrow light vector mesons omega and phi into a dilepton and a pseudoscalar pi-meson or eta-meson, respectively, are calculated. Thereby, all required parameters could be determined by other reactions so that one has predictive power for the considered decays. The calculated partial decay widths are in very good agreement with the experimental data.
A systematic method developed by the authors to evaluate the one-loop electromagnetic self-energies of the low-lying mesons is extended to the calculation of the vector sector including $ρ$, $ω$, and $ϕ$-mesons. The theoretical result of $ρ^0-ρ^\pm$ electromagnetic mass difference is in agreement with the measurements. An interesting effect called as electromagnetic mass anomaly of the massive Yang-Mills particles is further discussed. There is no new parameter in this study.
We use the 1/N_c method to estimate electromagnetic contributions to vector meson masses and mixings. We identify several new sources of rho-omega mixing coming from short-distance effects. We comment on the extraction of quark masses from the vector meson masses. We also present a simple group theoretical discussion of the electromagnetic mass differences.
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.
Modifications of the DGMLY relation for calculation of electromagnetic $π$-meson mass difference based on the Chiral Symmetry Restoration phenomenon at high energies as well as the Operator Product Expansion of quark densities for vector ($ρ$) and axial-vector ($a_1$) meson fields difference are proposed. In the calculations higher meson resonances in vector and axial-vector channels are taken into account. It is shown that the inclusion of the first $ρ$ and $a_1$ radial excitations improves the results for electromagnetic $π$-meson mass difference as compared with the previous ones. Estimatio…
Employing $U(3)_L\times U(3)_R$ chiral field theory, we find that Dashen's theorem, which holds for pseudoscalar mesons, can be generalized to the sector of axial-vector mesons, however, fails for vector mesons.
The electromagnetic structure of the pseudoscalar meson nonet is completely described by the sophisticated Unitary&Analytic model, respecting all known theoretical properties of the corresponding form factors.
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 relativistic calculations of the electromagnetic form factors and static moments of $ρ$-meson are given in the framework of the relativistic Hamiltonian dynamics with different model wave functions. The impulse approximation is used. Lorentz covariance and conservation law for the electromagnetic current operator are taken into account.
The Kroll-Lee-Zumino renormalizable Abelian quantum field theory of pionic strong interactions is used to compute the rho-meson propagator at the two-loop level.
It is shown that the diagonalization of the axial-vector -- pseudoscalar transitions in the effective meson Lagrangian in presence of electromagnetic interactions leads to a deviation from the vector meson dominance picture which usually arises in the Nambu - Jona-Lasinio model. The essential features of such modification of the theory are studied. Some important examples are considered in detail.
We calculate distributions of different vector mesons in purely exclusive ($p p \to p p V$) and semi-exclusive ($p p \to p X V$) processes with electromagnetic dissociation of a proton. The cross section for the electromagnetic dissociation is expressed through electromagnetic structure functions of the proton. We include the transverse momentum distribution of initial photons in the associated flux. Contributions of the exclusive and semi-exclusive processes are compared for different vector mesons ($V = ϕ, J/ψ, Υ$). We discuss how the relative contribution of the semi-exclusive processes dep…
In Ultra Relativistic Heavy-Ion Collisions (URHIC's) the light vector mesons play a crucial role in the description of hadronic interactions in a non-pertrubative QCD region. In this region efective hadron models use composite hadrons and mesons as field carriers instead of quarks and gluons. This theoretical review article tries to give a short way of understanding the underlying theory that we have for the conversion of vector mesons into photons together with the so-called Vector Dominance Model (VDM) and the electromagnetic form factors.
We calculate the cross sections for both electromagnetic and diffractive dissociation of protons for semiexclusive production of $J/ψ$ mesons in proton-proton collisions at the LHC. Several differential distributions in missing mass ($M_X$), or single-particle variables related exclusively to the $J/ψ$ meson are calculated for $\sqrt{s}$ = 7 TeV as an example. The cross sections and distributions are compared to the cross section of the purely exclusive reaction $p p \to p p J/ψ$. We show the corresponding ratio as a function of $J/ψ$ meson rapidity. We compare the distributions for purely ele…
A model is developed for electromagnetic form factors of the charged and neutral K-mesons. The formalism is based on ChPT Lagrangians with vector mesons. The form factors, calculated without fitting parameters, are in a good agreement with experiment for space-like and time-like photon momenta. Contribution of the two-kaon channels to the muon anomalous magnetic moment a_μis calculated.
The electromagnetic form factors of light and heavy pseudoscalar mesons are calculated within two covariant constituent-quark models, a light-front and a dispersion relation approach. We investigate the details and physical origins of the model dependence of various hadronic observables: the weak decay constant, the charge radius and the elastic electromagnetic form factor.
In this work we have employed Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz (CIA) to study electromagnetic decays of ground state equal mass vector mesons: $ρ$, $ω$, $ϕ$, $ψ$ and $Y$ through the process $V\rightarrowγ*\rightarrow e^+ + e^-$. We employ the generalized structure of hadron-quark vertex function $Γ$ which incorporates various Dirac structures from their complete set order-by-order in powers of inverse of meson mass. The electromagnetic decay constants for the above mesons are calculated using the leading order (LO) and the next-to-leading order (NLO) Dirac str…
Extended vector meson dominance model, that allows to describe the electromagnetic form factors of nucleons obeying the asymptotic quark counting rule prescriptions and contains the minimal number of free parameters, is presented. We get a reasonable fit of form factors over experimentally available space-like region of momentum transfer and get also reasonable results in the time-like region.
The contributions to heavy meson mass differences by the strong hyperfine interaction, the light quark masses and the electromagnetic interaction are obtained from the empirical values of the $D$, $D^*$, $B$ and $B^*$ masses by means of a mass formula based on the heavy quark mass expansion. The three different types of contributions are determined with significant accuracy to next to leading order in that expansion.
In the framework of $U(3)_L\times U(3)_R$ chiral field theory, Dashen's theorem is reexamined, and the well-known result of $m_{π^\pm}^2-m_{π^0}^2$ obtained by Das, Guralnik, Mathur, Low, and Young is reproduced. We find that Dashen's theorem, which automatically holds for pseudoscalar mesons in this theory, can be generalized to the sector of axial-vector mesons, however, fails for the sector of vector mesons.
A fully covariant model for describing the electromagnetic decay of Vector Mesons, both in light and in heavy sectors, is presented. The main ingredients of our approach are i) an Ansatz for the Bethe-Salpeter vertex for Vector Mesons, and ii) a Mandelstam-like formula for the electromagnetic decay constant. The free parameters of our approach are fixed through a comparison with the transverse momentum distribution obtained within a Light-Front Hamiltonian Dynamics framework with constituent quarks. Preliminary results for both the decays constants and the probability of the valence component …
We discuss a model for heavy mesons where the light quark (u or d) moves in the colour electric field from a heavy quark (c or b) placed in the center of the bag. We calculate energy spectra for pionic and photonic transitions from excited states. The transition amplitudes and the branching ratios between electromagnetic and pionic transitions compares favorable with the limited amount of known experimental data.
The electromagnetic contribution to the isomultiplet mass splittings of heavy mesons is reanalyzed within the framework of the heavy mass expansion. It is shown that the leading term in the expansion is given to a good approximation by the elastic term. $1/m_{Q}$-corrections can only be estimated, the main source of uncertainty now being inelastic contributions. The $1/m_{Q}$-corrections to the elastic term turn out to be relatively small in both D and B pseudoscalar mesons.
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.
Rare electromagnetic decays of charmed mesons are useful laboratories to explore the structure of hadronic states and the interactions between photon and charmed mesons, to test the chiral perturbation theory in flavor sector and to search for new physics including dark photons. In this paper, we calculate the relative branching ratios of electromagnetic Dalitz decays $D_{(s)}^\ast\to D_{(s)}\ell^+\ell^-$ to their corresponding radiative decays $D_{(s)}^\ast\to D_{(s)}γ$, the dileptonic invariant mass spectra and the leptonic angular distributions with transition form factor in Vector-Meson Do…
The main assumption of the model is that in soft processes mesons behave like systems made of valence quarks and an effective vacuum- like field. The 4-momentum of the latter represents the relativistic generalization of the potential energy. The electromagnetic form factors are expressed in terms of the overlap integral of the initial and final wave functions written under the form of Lorentz covariant distribution of quark momenta. The calculation is fully Lorentz covariant and the form factors of the charged mesons are normalized to unity at t=0.
The electromagnetic (EM) form fators of the pseudoscalar and vector mesons are calculated in the light-front framework. We extract these form factors from the relevant matrix elements directly, instead of choosing the Breit frame. The results show that the charge radius of the meson are related to both the first and second longitudinal momentum square derivative of the momentum distribution function. In addition, the static properties of the EM form factors and the heavy quark symmetry of the charge radii are checked analytically when we take the heavy quark limit.
The decays of narrow light vector mesons into pseudoscalar mesons and dileptons are calculated to leading order in a recently proposed scheme which treats pseudoscalar and vector mesons on equal footing. Since all required parameters have been determined by other reactions the presented approach gains predictive power for the considered processes. The decay of the $ω$-meson into pion and dimuon agrees reasonably well with the available experimental data concerning form factor, single-differential decay width and partial decay width. As well do the partial decay width of the $ω$-meson into a pi…
Electromagnetic splittings for mesons and baryons are calculated in a formalism where the constituent quarks are considered as dressed quasiparticles. The electromagnetic interaction, which contains coulomb, contact, and hyperfine terms, is folded with the quark electrical density. Two different types of strong potentials are considered. Numerical treatment is done very carefully and several approximations are discussed in detail. Our model contains only one free parameter and the agreement with experimental data is reasonable although it seems very difficult to obtain a perfect description in…
A simple, but fully-covariant model for describing neutral Vector Mesons, in both light and heavy sectors, is briefly illustrated. The main ingredients of our relativistic constituent model are i) an Ansatz for the Bethe-Salpeter vertex for Vector Mesons, and ii) a Mandelstam-like formula for the electromagnetic decay widths. The free parameters of our approach are fixed through a comparison with the valence transverse-momentum distribution, $n(k_\perp)$, obtained within phenomenological Light-Front Hamiltonian Dynamics models reproducing the mass spectra. Preliminary results for the transvers…
The electromagnetic form factors of the $ρ$ meson are evaluated adopting a relativistic constituent quark model based on the light-front formalism, and using a meson wave function with the high-momentum tail generated by the one-gluon-exchange interaction. The breakdown of the rotational covariance for the one-body component of the current operator is investigated and the sensitivity of the ratio of the $ρ$-meson form factors to the pion (charge) form factor to the spin-dependent component of the effective $q \bar{q}$ interaction is illustrated.
We calculate the $π$, $ρ$, $ω$, and $γ$ coupling constants between the heavy meson doublets $(1^-,2^-)$ and (0^-,1^-)/(0^+,1^+) within the framework of the light-cone QCD sum rule at the leading order of heavy quark effective theory. Most of the sum rules are stable with the variations of the Borel parameter and the continuum threshold. Then we calculate the strong and electromagnetic decay widths of the $(1^-,2^-)$ D-wave heavy mesons. Their total widths are around several tens of MeV, which is helpful in the future experimental search.
We investigate the electromagnetic form factors of the (rho) meson in light cone QCD sum rules. We find that the ratio of the magnetic and charge form factors is larger than two at all values of Q^2, (Q^2 >= 0.5 GeV^2). The values of the individual form factors at fixed values of Q^2 predicted by the light cone QCD sum rules are quite different compared to the results of other approaches. These results can be checked in future, when more precise data on (rho) meson form factors is available.
Based on the recently measurements of the $e^{+} e^{-} \to Σ^{+} \barΣ^{-}$ and $e^{+} e^{-} \to Σ^{-} \barΣ^{+}$ processes, the electromagnetic form factors of the hyperon $Σ^+$ and $Σ^-$ in the timelike region are investigate by using the vector meson dominance model. We have included the contributions from the $ρ$, $ω$ and $ϕ$ mesons. The model parameters are determined with the BESIII experimental data on the timelike effective form factors $|G_{\rm eff}|$ of $Σ^{+}$ and $Σ^{-}$ for center-of-mass energy from 2.3864 to 3.02 GeV. Then, we analytically continue the electromagnetic form facto…
In this article, we calculate the electromagnetic form-factor of the $π$ meson with the light-cone QCD sum rules. The numerical value $F_π^{p}(0) =0.999\pm 0.001$ is in excellent agreement with the experimental data (extrapolated to the limit of zero momentum transfer, or the normalization condition $F_π(0)=1$). For large momentum transfers, the values from the two sum rules are all comparable with the experimental data and theoretical estimations.
We investigate the pion electromagnetic charge radii and mass dropping of the rho meson at finite density. We first calculate the pion charge radii within the framework of the nonlocal chiral quark model from the instanton vacuum both at zero and finite densities. In order to relate the change of the pion charge radius to that of the rho-meson mass at finite density, we employ the vector-meson dominance for the pion electromagnetic form factor. It turns out that the pion charge radius is getting larger as the quark chemical potential increases. As a result, the rho-meson mass falls off as the …
The pure annihilation type decays $B^0_d\toϕγ$ and $B_s\toργ$ receive only color suppressed penguin contributions with a very small branching ratio in the standard model. When we include the previously neglected electromagnetic dipole operator, the branching ratios can be enhanced one order magnitude larger than previous study using QCD factorization approach. That is ${\cal BR}(\bar B^0_d\toϕγ)\simeq 1 \times 10^{-11}$ and ${\cal BR}(B_s\toργ) \sim (6-16)\times 10^{-10}$. The new effect can also give a large contribution, of order $10^{-9}$, to transverse polarization of $B\toϕρ$ and $B\to ωϕ…
The space-like electromagnetic form factor is expressed in terms of the overlap integral of the initial and final meson wave functions written as Lorentz covariant distributions of internal momenta. The meson constituents are assumed to be valence quarks and an effective vacuum-like field. The momentum of the latter represents a relativistic generalization of the potential energy of the quark system. The calculation is fully Lorentz covariant and the form factors of the charged mesons are normalized to unity at t=0. The numerical results have been obtained by freezing the transverse degrees of…
The electromagnetic transition form factors of $η$ and $η'$ are calculated in the light-cone perturbation theory. We show that it is unreliable to determine the η-\etap'$ mixing angle without any additional normalization conditions other than their decay widthes to two photons. The possible intrinsic $c\bar{c}$ component in the flavor singlet is investigated. The heavy quark pair has distinct properties from the light ones in electromagnetic transition processes of pseudoscalar mesons. It is possible to explore the size of $c\bar{c}$ component and our numerical results disfavor a large portion…
The $t$-channel contribution to the difference of electromagnetic polarizabilities of the nucleon, $(α-β)^t$, can be quantitatively understood in terms of a $σ$-meson pole in the complex $t$-plane of the invariant scattering amplitude $A_1(s,t)$ with properties of the $σ$ meson as given by the quark-level Nambu--Jona-Lasinio model (NJL). Equivalently, this quantity may be understood in terms of a cut in the complex $t$-plane where the properties of the $σ$ meson are taken from the $ππ-> σ-> ππ$, $γγ-> σ-> ππ$ and $N\bar{N} -> σ-> ππ$ reactions. This equivalence may be understood as a sum rule …
The study of two-pseudoscalar and two-photon decays for the scalar meson nonet below 1 GeV is performed within an effective approach in which the scalar resonances are described as (Jaffe's) tetraquark states. The dominant (fall apart decay) and the subdominant (one transverse gluon as intermediate state) decay amplitudes are systematically taken into account. The latter improves the agreement with the experimental data. Possible scenarios concerning the scalar-isoscalar mixing are discussed.
In this paper we calculate the next-to-leading-order (NLO) corrections to $ρ$-meson electromagnetic form factors by employing the $k_T$ factorization approach. We find that the NLO correction to $F_i (Q^2)(i=LT,TL)$ is around $30\%$ of the leading-order (LO) contributionin the region $Q^2>2GeV^2$. The NLO correction to $F_{LL}(Q^2)$ is close to $20\%$ of the LO one in the region $Q^2>3GeV^2$. The NLO radiative corrections to the electric, magnetic, and quadruple form factors $F_j(Q^2) (j=1,2,3)$ are sizeable in magnitude and agree with those from other approaches.
We apply the light-cone technique to electroproduction reaction $ep\to eπ^+n$ long considered as a means of measuring the electromagnetic form factor of the pion. We show that the interpretation of the long-standing puzzle of large transverse cross section ($σ_T$) in terms of the $γ^*ρ\to π$ transition on the $ρ$ mesons in the light-cone proton is possible, but requires quite a slow decrease of the $F_{ρπ}(\q2)$ form factor. This interpretation can be tested in the related $ep\to eπ^0p$ reaction. Corrections which are due to the final-state meson-baryon interactions (FSI) are evaluated and are…
We investigate the elastic form factors of the rho meson in the light-front quark model(LFQM). With the phenomenologically accessible meson vertices including the one obtained by the Melosh transformation frequently used in the LFQM, we find that only the helicity $0\to 0$ matrix element of the plus current receives the zero-mode contribution. We quantify the zero-mode contribution in the helicity $0\to 0$ amplitude using the angular condition of spin-1 system. After taking care of the zero-mode issue, we obtain the magnetic($μ$) and quadrupole($Q$) moments of the rho meson as $μ=1.92$ and $Q=…
It has been previously shown that a particular nonperturbative constituent-quark model of hadrons describes experimental measurements of electromagnetic form factors of light charged mesons through a small number of common phenomenological parameters, matching at the same time the Quantum-Chromodynamics (QCD) asymptotics for the pi-meson form factor at large momentum transfer. Here we start with the determination of the K0 electromagnetic form factor in this approach. Precise measurement of the K0 charge radius makes it possible to constrain model parameters with high accuracy. Then, with all …
The assignments of the isoscalar scalar mesons f0(980), f0(1370), and f0(1500) in terms of their qqbar substructure is still a matter of heated dispute. Here we employ the weak and electromagnetic decays D(s)(+) to f0+pi(+) and f0 two-photon decays, respectively, to identify the f0(980) and f0(1500) as mostly ssbar, and the f0(1370) as dominantly nonstrange, in agreement with previous work. The two-photon decays can be satisfactorily described with quark as well as with meson loops, though the latter ones provide a less model-dependent and more quantitative description.
We investigate electromagnetic corrections to the rare $B$-meson leptonic decay $B_{s,d} \to μ^+μ^-$ from scales below the bottom-quark mass $m_b$. Contrary to QCD effects, which are entirely contained in the $B$-meson decay constant, we find that virtual photon exchange can probe the $B$-meson structure, resulting in a "non-local annihilation" effect. We find that this effect gives rise to a dynamical enhancement by a power of $m_b/Λ_{\rm QCD}$ and by large logarithms. The impact of this novel effect on the branching ratio of $B_{s,d}\toμ^+μ^-$ is about $1\%$, of the order of the previously e…
We show that the electromagnetic superconductivity of vacuum in strong magnetic field background is consistent with the Vafa-Witten theorem because the charged vector meson condensates lock relevant internal global symmetries of QCD with the electromagnetic gauge group.
Using baryon chiral perturbation theory including vector mesons, we analyse various continuum contributions to the isoscalar electromagnetic spectral functions of the nucleon induced by the leading order couplings.
The isospin symmetry breakings of q{\bar q} are investigated in the QCD sum rule method. The electromagnetic effects are evaluated following the procedure requiring that the electromagnetic effects for charged meson be gauge invariant. We find that the electromagnetic effects are also dominant in the isospin violations of rho meson, which have been shown to be the case in the mass splittings of pions. The numerical results for the difference of pion decay constants and the masses of rho mesons are presented, which are consistent with the data.
Double integral representation in the invariant masses of a composite system and nonperturbative calculation of the asymptotics of light-meson electromagnetic form factors
Samara State Technical University（萨马拉国立技术大学）；Lyceum 135 - basic school of the Russian Academy of Sciences（俄罗斯科学院第135中学）；D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University（莫斯科国立大学D.V.斯科别尔琴核物理研究所）
Motivated by the planned measurements of the time-like electromagnetic proton form factors an exploratory study of the time-like electromagnetic pion form factor is presented in a formalism which describes mesons as Poincaré-invariant bound states. In the respective quark interaction kernel, beyond the gluon-intermediated interactions for valence-type quarks, non-valence effects are included by allowing the pions to couple back in a self-consistent manner to the quarks. Consequently, the opening of the dominant $ρ$ decay channel, $ρ\to ππ$, and the presence of a multi-particle branch cut, sett…
We perform an analysis on the electromagnetic form factors of the $Λ$ hyperon in the time-like reaction $e^+e^-\rightarrow Λ\barΛ$ by using a modified vector meson dominance model. We consider both the intrinsic structure components and the meson clouds components. For the latter one, we not only include the contributions from the $ϕ$ and $ω$ mesons, but also take into account the contributions from the resonance states $ω(1420)$, $ω(1650)$, $ϕ(1680)$ and $ϕ(2170)$. We extract the model parameters by combined fit to the time-like effective form factor $|G_{\rm{eff}}|$, the electromagnetic form…
We calculate rates for hybrid meson production by electromagnetic and weak interactions in the flux-tube model. Applications include photo and electroproduction at Jefferson Laboratory and HERA, and the production of light strange and charmed hybrids in the weak decays of heavy flavours. Photoproduction of some light hybrids is predicted to be prominent in charge exchange reactions, $γp \to n \cal{H}$ and accessible in $γp \to p \cal{H}$. Production of light or charmed hybrids in $B$ and $D$ decays may be feasible with high statistics. Photoproduction of the axial hybrid meson is predicted to …
We investigate the effect of the electromagnetic field generated in relativistic heavy-ion collisions on the dissociation of $Υ$ mesons. The electromagnetic field is calculated using a simple model which characterizes the emerging quark-gluon plasma (QGP) by its conductivity only. A numerical estimate of the field strength experienced by $Υ$ mesons embedded in the expanding QGP and its consequences on the $Υ$ dissociation is made. The electromagnetic field effects prove to be negligible compared to the established strong-interaction suppression mechanisms.
We apply a modified vector meson dominance (VMD) model to analyze the electromagnetic form factors of the $Λ_c$ hyperon in the time-like reaction $e^+e^-\rightarrow Λ_c^+ \barΛ_c^-$. In the model, we include the contributions from the vector charmed mesons and their excitations $ψ(1S)$, $ψ(2S)$, $ψ(3770)$, $ψ(4040)$, $ψ(4160)$ and $ψ(4415)$. We perform a combined fit to the available data on the Born cross section in reaction $e^+e^-\rightarrow Λ_c^+ \barΛ_c^-$ and the ratio of the electromagnetic form factors $|G_E/G_M|$ to obtain the values of the model parameters. Our results show that the …
