Meson Dominance Model Research Articles

Exotic mesons and the hadronic energy momentum tensor

It is argued that SU(3)-singlet exotic (i.e. built of two or more quark-antiquark pairs) tensor mesons make large contributions to matrix elements of the energy-momentum tensor. An apparent inconsistency between meson dominance models and exchange degeneracy is thereby removed. New predictions about exotic meson couplings follw.

Comparison of pion electroproduction data with vector meson dominance predictions

Single pion electroproduction results are compared with predictions obtained within the vector meson dominance model. The large longitudinal contribution observed in pion electroproduction is successfully predicted from data on pion photoproduction and on production of vector mesons by pions from nucleons.

Measurement of proton compton scattering at 6 GeV and small momentum transfers

Compton scattering on protons has been measured at a mean photon energy of 6 GeV and four-momentum transfers − t between 0.06 and 0.60 (GeV/ c) 2. The differential cross section shows a diffraction-like behaviour. The cross section extrapolated to t=0 is in fair agreement with the optical point. Discrepancies with the vector meson dominance model are pointed out.

General analysis of the vector meson-dominance model predictions for meson decays

Using the vector-meson dominance model,SU3 symmetry and the ω-ϕ and η-X0 mixing hypotheses (recent results seem to contradict the possibility of a mixing between the η and the E (1420)-meson) the decays of the pseudoscalar and the vector mesons are systematically investigated. The explicit expressions for phase-space evaluations are listed. The predictions of the model concerning the branching ratios and decay rates are discussed in detail, classifying those which are independent of some coupling constants, mixing angles and (or) experimental inputs. A consistent picture is obtained for the π0→γγ and the ω→π0γ decay modes and the ω and ϕ branching ratios and a resonable agreement is generally found with the experimental situation, which is sometimes rather unclear. Our results seem to disagree with a recent determination of the branching ratios of the ω→хγ and ω→π0π0γ decay modes.

A sum rule for the I=0, s-wave phase shift in meson-meson scattering from broken liouville symmetry

Starting from the equal-time commutators of the time-dependent generators D( x o ) and K μ ( x o ), μ = 0, 1, 2, 3, of the dilatations and the special Liouville (conformal) transformations with the interpolating fields ϕ α ( x) of scalar or pseudoscalar hadrons, it is possible to derive an interesting sum rule for the I=0, s-wave scattering phase shift of these mesons. The sum rule shows - among other things - that the dimension of length of the fields ϕ α ) x) is intimately related to the number of resonances in their I=0, s-wave scattering channel: Canonical field theory predicts three such resonances. Finally, a scalar meson dominance model for the divergence of the dilatation current gives relations between several quantities of these resonances.

Pion electroproduction and choice of frame in the vector meson-dominance model

It is pointed out, how forthcoming experiments on electroproduction of pions will provide additional information on the choice of the reference frame to be used to formulate the mass-extrapolation assumption of the VDM in pion-production processes.

Pion electroproduction and choice of frame in the vector meson-dominance model

Pion electroproduction and choice of frame in the vector meson-dominance model

Vector meson dominance and photoproduction

A brief review of the basic principles of the vector meson dominance model is given. The model is then compared with most recently obtained experimental results. It is stressed that it provides a simple and unified interpretation of photoproduction of hadrons at high energies.

π + production with linearly polarized photons

Single π + production on protons by linearly polarized photons of 2.5 to 5 GeV was measured at squared four momentum transfers t between −0.01 and −0.6 (GeV/ c) 2. The results show that the differential cross section dσ ⊥ dt with the electric vector of the photon perpendicular to the reaction plane is much larger than dσ ‖ dt with the electric vector parallel to the reaction plane. The predictions of Regge models and of the vector meson dominance model are briefly discussed.

Comparison of Orsay results on vector mesons with the vector meson dominance model predictions

Results of the three Orsay experiments are analyzed in the vector meson dominance hypothesis. The coupling constants of ϱo, ωo and φo mesons to the photons are determined, and the mixing angle θ Y and θ N of the ωo and φo mesons are calculated. Our values are compared to various theoretical predictions.

The shape of mesons

From Chou-Yang's model for high-energy scattering numerical values of the form factors π, K, ϱ, ω, φ are deduced in analogy to the proton form factor. It is concluded that (i) the π, K form factors are incompatible with the naive vector meson dominance model for t ≠ 0, and (ii) the process γ+p → φ+p is crucial to the validity of the model. Further it is pointed out that the qualitative features of the results are valid for other similar models as well.

Vector meson dominance model and π± production by unpolarized and linearly polarized photons

Using the vector meson dominance model, it is shown that the polarization of vector mesons produced in meson nucleon collisions yields information on pion production by linearly polarized photons. Combining vector dominance and a quark-model relation the cross section for charged pion production by linearly polarized photons is predicted. Moreover, the unpolarized π ± cross sections calculated from the vector dominance and quark models are compared with recent experiments.

On the photoproduction of multipion systems

Combining vector meson dominance and quark model with isospin independence of production reactions above the resonance region, we predict the cross-sections for multipion photoproduction from the corresponding π -N data.