Coupling Constants Of Vector Mesons Research Articles

There is only one set of the correct values of fF, fD and fS coupling constants in SU(3) invariant Lagrangian of the vector-meson-baryon interactions

One can prove, there is generally eight various ω − ø mixings forms in elementary particle physics, which on one side give different forms of the vector-meson-nucleon coupling constants through fF, fD and fS in SU(3) invariant Lagrangian of the vector-meson-baryon interactions, and on the other side different signs of the universal vector-meson coupling constants fρ, fω and fø. Identical set of numerical values of fF, fD and fS is evaluated only in that case, if the same ω − ø mixing is applied to a derivation of the vectormeson-nucleon coupling constant forms and also to the signs of the universal vector-meson coupling constants fρ, fω and fø.

Dispersion theoretical analysis of the nucleon form factors

We review the achievements of the project C.2 , that deals with a dispersion theoretical analysis of the nucleon form factors. We have analyzed the world data for the space-like and time-like form factors to extract nucleon radii and vector meson coupling constants. Our proton charge radius r P E ≃ 0.85 fm has gained prominence in the so-called proton radius puzzle, see Ref. [1]. We also have analyzed the strong energy dependence of the e + e − → pp amplitude at the nucleon-antinucleon threshold, two-photon exchange effects and isospin violation in the isovector nucleon form factors.

Numerical values of thefF,fD, andfScoupling constants in the SU(3) invariant interaction Lagrangian of the vector-meson nonet with1/2+octet baryons

It is demonstrated how an utilization of all existing experimental information on electric and magnetic nucleon form factors, to be described by the Unitary and Analytic (U\&A) nucleon electromagnetic structure model in space-like and time-like regions simultaneously, can provide numerical values of $f^F$, $f^D$, $f^S$ coupling constants in $SU(3)$ invariant interaction Lagrangian of the vector-meson nonet with $1/2^+$ octet baryons. The latter, together with universal vector-meson coupling constants $f_V$, play an essential role in a prediction of $1/2^+$ octet hyperon electromagnetic form factors behaviors.

QCD sum rules for the coupling constants of vector mesons to octet baryons

The QCD sum rules on the light cone proposed by Wang for the coupling constants of the ρ meson are generalized to the vector mesons ω and φ and all octet baryons, the Λ-hyperon included. A comparison with other results is given.

Parity-violating asymmetry in theHe3(n⃗,p)H3reaction

The longitudinal asymmetry induced by parity-violating (PV) components in the nucleon-nucleon potential is studied in the charge-exchange reaction $^{3}\mathrm{He}$($\mathrm{nP\vec},p$)$^{3}\mathrm{H}$ at vanishing incident neutron energies. An expression for the PV observable is derived in terms of $T$-matrix elements for transitions from the ${}^{2S+1}{L}_{J}={}^{1}{S}_{0}$ and ${}^{3}{S}_{1}$ states in the incoming $n$-$^{3}\mathrm{He}$ channel to states with $J=0$ and 1 in the outgoing $p$-$^{3}\mathrm{H}$ channel. The $T$-matrix elements involving PV transitions are obtained in first-order perturbation theory in the hadronic weak-interaction potential, while those connecting states of the same parity are derived from solutions of the strong-interaction Hamiltonian with the hyperspherical-harmonics method. The coupled-channel nature of the scattering problem is fully accounted for. Results are obtained corresponding to realistic or chiral two- and three-nucleon strong-interaction potentials in combination with either the DDH or pionless EFT model for the weak-interaction potential. The asymmetries, predicted with PV pion and vector-meson coupling constants corresponding (essentially) to the DDH ``best values'' set, range from --9.44 to --2.48 in units of ${10}^{\ensuremath{-}8}$, depending on the input strong-interaction Hamiltonian. This large model dependence is a consequence of cancellations between long-range (pion) and short-range (vector-meson) contributions and is of course sensitive to the assumed values for the PV coupling constants.

A practical guide to unravel time-like transition form factors

A method to determine masses, widths and coupling constants of vector mesons, like $ \phi$ (1020) , $ \omega$ (782) and $ \rho^{0}_{}$ (770) recurrences is defined. Starting from data on decay rates and cross-sections for the processes: $ \phi$ → M I $ \gamma$ , $ \phi$ → M I e + e - and e + e - → M I $ \phi$ , where MI is a pseudoscalar or scalar meson with isospin I = 0, 1 , the time-like transition form factors, which describe the vertex $ \phi$ $ \gamma$ M I , are parameterized using a vector-meson-propagators description in the low-energy region ( < 3-4 GeV), the quark-counting rule prescription for the high-energy behavior, and the analyticity imposed by means of the dispersion relations.

Electromagnetic Transition Form Factors and Dilepton Decay Rates of Nucleon Resonances

Relativistic, kinematically complete phenomenological expressions for the dilepton decay rates of nucleon resonances with arbitrary spin and parity are derived in terms of the magnetic, electric, and Coulomb transition form factors. The dilepton decay rates of the nucleon resonances with masses below 2 GeV are estimated using the extended vector meson dominance (VMD) model for the transition form factors. The model provides a unified description of the photo- and electroproduction data, γ(γ*)N→N*, the vector meson decays, N*→Nϕ(ω), and the dilepton decays, N*→Nℓ+ℓ−. The constraints on the transition form factors from the quark counting rules are taken into account. The parameters of the model are fixed by fitting the available photo- and electroproduction data and using results of the multichannel partial-wave analysis of the π N scattering. Where experimental data are not available, predictions of the non-relativistic quark models are used as an input. The vector meson coupling constants of the magnetic, electric, and Coulomb types are determined. The dilepton widths and the dilepton spectra from decays of nucleon resonances with masses below 2 GeV are calculated.

General form of hybrid derivative coupling to study dense nuclear matter and its phase transition to quark matter

We propose a general form of hybrid derivative coupling model of scalar mesons to various baryons in a field theoretical model to study nuclear matter. The strength of Yukawa point coupling and that of derivative coupling of scalar mesons to various baryons are taken in a suitable proportion characterized by a hybridization parameter \ensuremath{\alpha}. Analytical relations are set up which express scalar and vector meson coupling constants, compression modulus and the parameter \ensuremath{\alpha} in terms of empirical values for effective nucleon mass, energy per nucleon, and baryon density of normal nuclear matter. Density expansions of effective nucleon mass and energy per nucleon, incorporating terms up to eighth power in nuclear matter density, are given. We study equation of states of dense nuclear matter at zero temperature considering \ensuremath{\Delta} resonances. We also investigate the phase transition from highly compressed nuclear matter to quark matter and its dependence on hybridization parameter \ensuremath{\alpha} and also on coupling constants involving mesons and \ensuremath{\Delta}'s. We determine equilibrium pressure, chemical potential, ``phase transition density,'' baryon densities, and energy densities of hadronic matter and quark matter which characterize the phase transition region. We also briefly discuss linear response of the nuclear system in the present model.

Unified QCD determination of all vector meson coupling constants

Coupling constants of all vector mesons are determined in QCD by means of a new QCD sum-rule method. The results are found to be sensitive to the binding energy (i.e. meson and quark mass differences). For standard values of quark masses we obtainf ϱ=202 MeV,f K*=216 MeV,f D*=212±22 MeV,f B*=138±42 MeV, $$f_{D_s^* } = 238 \pm 21\,MeV$$ and $$f_{B_s^* } = 163 \pm 45\,MeV$$ . Based on this approach the spin-flavour symmetry for the heavy quark systems are also discussed.

Vector-meson-exchange and unitarity effects in low-energy photoproduction

Vector-meson-exchange effects are investigated for photoproduction in the $\ensuremath{\Delta}$ region. An improved analysis using a current-algebra model with unitarity corrections and the most recent multipole analysis indicates the necessity of vector-meson contributions. The required vector-meson coupling constants are consistent with quark-model values.

Relativistic calculation of nuclear matter and the nuclear surface

Relativistic mean field Hartree and Thomas-Fermi calculations are made for infinite and semiinfinite symmetric nuclear matter. Cubic and quartic scalar meson self-interactions are included. The strength of these self-interactions, the scalar and vector meson coupling constants, and the scalar meson mass are considered as parameters chosen to fit the empirical properties of nuclear matter and of the nuclear surface. Acceptable fits imply large self-interactions. No abnormal nuclear matter solutions are found. The best fit of the nuclear surface yields a compressibility coefficient of 150 ± 50 MeV. The Hartree and TF results are in good agreement for larger surface thicknesses.

OBEP and eikonal form factor: (I). Results for two-nucleon data

A new niomentum-space one-boson-exchange potential is presented in which the phenomenological cut-off of dipole type used so far has been replaced by a form factor obtained from an eikonal approximation to multiple vector meson exchange processes. A good description of the NN scattering phase parameters ( χ 2 = 2.77) and deuteron data ( E b = 2.2246 MeV, Q = 0.2864 fm 2, P D = 4.32%) is obtained using vector meson coupling constants which are much smaller compared to former OBE models and thus are closer to determinations from other sources. This nice feature is traced back to the special structure of the eikonal form factor.

A possible method of testing the universality of strong interactions

It is shown that the cross-section of the process π − + p → n + e + + e − at the effective mass e +e −-system m 2 ⪅ m π 2 has the same order of magnitude as at m 2 = m ϱ 2 and is very sensitive to the universality relation of coupling constants of vector mesons.

Zero-Parameter Model of theN−NPotential

We present a theoretical $N\ensuremath{-}N$ potential containing, in addition to the one-pion-exchange contribution, vector-meson-exchange terms and contributions due to the inelastic interactions $N+N\ensuremath{\rightarrow}N+\ensuremath{\Delta}(1236)$ and $N+N\ensuremath{\rightarrow}\ensuremath{\Delta}(1236)+\ensuremath{\Delta}(1236)$. There are no adjustable parameters in this calculation, which otherwise, however, suffers from most of the usual shortcomings and difficulties of few-particle-exchange models for strong-interaction processes. The vector-meson coupling constants are fixed by electromagnetic form factors and backward vector-meson production data, while the phenomenological constants in the inelastic contributions to the potentials have been fixed by the experimental data on the inelastic reactions themselves. Our results are found to be in qualitative agreement with phenomenological potentials obtained by Reid from the $N\ensuremath{-}N$ scattering data. We also calculate the vector-meson-exchange potentials for all $B\ensuremath{-}B$ and $B\ensuremath{-}\overline{B}$ states with $J\ensuremath{\le}2$. Our results indicate that the $B\ensuremath{-}B$ interaction will contain a short-range repulsion in all states of practical interest aside from the $T=1\ensuremath{\Xi}\ensuremath{-}N$ state which is discussed. We find strong attractions in most of the $\mathrm{SU}(3)$ singlet and octet $B\ensuremath{-}\overline{B}$ states.

Bjorken Limit and Sum Rules for theπ0Lifetime and theρωπCoupling Constant

The Bjorken limit is applied to obtain sum rules for the lifetime of ${\ensuremath{\pi}}^{0}$ and for the vector-meson coupling constants. In particular we obtain predictions that $\frac{{{g}_{\ensuremath{\rho}\ensuremath{\omega}\ensuremath{\pi}}}^{2}}{4\ensuremath{\pi}}=0.53\ifmmode\pm\else\textpm\fi{}0.1$ and ${\ensuremath{\tau}}_{{\ensuremath{\pi}}^{0}}\ensuremath{\simeq}(0.84\ifmmode\pm\else\textpm\fi{}0.83)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ sec. The latter is in good agreement with the experimental value (0.89\ifmmode\pm\else\textpm\fi{}0.18)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ sec. From our knowledge of the approximate value of ${g}_{\ensuremath{\rho}\ensuremath{\omega}\ensuremath{\pi}}$, we conclude that the high-energy behavior of the ${\ensuremath{\pi}}^{0}\ensuremath{\gamma}\ensuremath{\gamma}$ vertex function is not important to the pion lifetime. The results of this calculation constitute a consistency condition on the plausibility of the Bjorken limit.

Peripheral Production and Decay of Resonances in High-Energy Meson-Nucleon Collisions

Data on quasi-two-body reactions initiated by high-energy meson-nucleon collisions are analyzed from the viewpoint of the peripheral model. The basic interaction mechanism is assumed to be pseudoscalar and/or vector exchange, and absorptive effects arising from coupling between different channels are taken into account. Excellent agreement is found between the one-pion-exchange model and the production and decay data for the processes ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}p$ for incident momenta from \ensuremath{\sim}2 to 8 GeV/c. A unified analysis of the reactions ${K}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{K}^{*\ifmmode\pm\else\textpm\fi{}}p$ at 3 GeV/c, and ${K}^{+}n\ensuremath{\rightarrow}{K}^{0}p$ at 2.3 GeV/c, is presented; a single pair of vector coupling constants is able to account for the various angular distributions of production. The theory predicts, and preliminary data confirm, appreciable momentum-transfer dependence of the ${K}^{*}$ spin-density matrix. Equally satisfactory fits to the data are found for ${K}^{+}p\ensuremath{\rightarrow}{K}^{0}{N}^{*++}$ at 3 GeV/c, ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{Y}^{*}$ (1385) at 2.24 GeV/c, and ${\ensuremath{\pi}}^{+}n\ensuremath{\rightarrow}\ensuremath{\omega}p$ at 3.25 GeV/c. In the latter reaction the absorption model reproduces the large departure of the $\ensuremath{\omega}$-decay correlations from those characteristic of $\ensuremath{\rho}$ exchange in the absence of absorption. The model cannot explain why the differential cross section for ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{N}^{*}$ is considerably narrower than for ${K}^{+}p\ensuremath{\rightarrow}{K}^{0}{N}^{*}$. The theoretical momentum-transfer distributions and decay correlations for double resonance production ($\ensuremath{\pi}p\ensuremath{\rightarrow}\ensuremath{\rho}{N}^{*}$, $\mathrm{Kp}\ensuremath{\rightarrow}{K}^{*}{N}^{*}$) are in general agreement with the data, as are the results on combined decay correlations of $\ensuremath{\rho}$ and ${N}^{*}$ in ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{N}^{*}$. But the calculated absolute cross sections are considerably larger than observed, probably because the model fails to include the requirements of unitarity, important when the couplings are large. The determination of vector-meson coupling constants is discussed. Because of fundamental difficulties associated with vector-meson exchange amplitudes at high energies, it is concluded that important refinements of the model are necessary if such coupling constants are to be inferred from the data.