Photoproduction Of Vector Mesons Research Articles

Photoproduction of vector mesons on protons at energies up to 5.8 GeV

Results for the reactions γp → p ϱ 0, γp → p ϱ 0 π + π −, γp → p ω, γp → p ωπ + π −, γp → p ø, γp → p øπ + π − are presented.

Composite Models of Hadrons and High Energy Photoproduction of Vector Mesons

Composite Models of Hadrons and High Energy Photoproduction of Vector Mesons

High-Energy Photoproduction Branching Ratios in the Regge-Pole Model

Photoproduction of pseudoscalar, vector, and tensor mesons at high energies is formulated in a Reggepole model incorporating $\mathrm{SU}(3)$ symmetry. The exchanged Regge poles are the vector and tensor trajectories satisfying broken $\mathrm{SU}(3)$ and unbroken $\mathrm{SU}(3)$ couplings with the same classification as given previously. From this formalism simple branching ratios are predicted which can be tested with future experimental results.

Photoproduction of vector mesons as virtual vector meson-proton scattering: Addendum

Photoproduction of vector mesons as virtual vector meson-proton scattering: Addendum

Pomeranchuk-Exchange Contribution to Forward Photon Processes

Assuming pure Regge-pole behavior and the crossing relations for helicity amplitudes, we show that (1) the Pomeranchuk trajectory does not contribute to Compton scattering from spin-0 or spin-\textonehalf{} particles in the forward direction; (2) Pomeranchuk exchange does contribute to forward vector-meson photoproduction, and at high energies the production of vector mesons with helicity\ifmmode\pm\else\textpm\fi{}1 dominates over the production of those with zero helicity. Some interesting properties of the crossing relations are derived and used to obtain these results. We briefly discuss the difficulties associated with conclusion (1).

Implications of Regge Behavior for Processes Involving Photons

Properties of the crossing matrix for helicity amplitudes are enumerated and then exploited in a simple Regge-pole model of photon-hadron interactions. We find that: (1) The vacuum or Pomeranchuk trajectory is absent in forward Compton scattering of real photons on nucleons or pions. Thus the total nuclear cross section for photons or nucleons should vanish asymptotically. (2) The amplitudes entering the forward spin-flip Compton scattering of virtual photons on protons, which are crucial in the proton structure contributions to the ground-state hyperfine splitting (hfs) in hydrogen, may be chosen so that they do not require a subtraction when writing dispersion relations for them in the energy variable. One must look elsewhere than to the high-energy behavior of the amplitudes for the erasure of the discrepancy between theory and experiment on the hfs. (3) In forward photoproduction of vector mesons on protons, the polarization of the mesons should be predominantly longitudinal at "high energy." (4) In the differential cross section $\frac{d\ensuremath{\sigma}}{\mathrm{dt}}$ for photoproduction of neutral pions, there should be a dip at $t\ensuremath{\approx}\ensuremath{-}0.5$ Be${\mathrm{V}}^{2}$ because of a nonsense zero in all crossed-channel helicity amplitudes.

Phenomenological Analysis of the Photoproduction of Neutral Vector Mesons and Strange Particles

Branching ratios for photoproduction of vector mesons and strange particles are discussed. The one-pion-exchange mechanism cannot explain the observed ratio between $\ensuremath{\rho}$ and $\ensuremath{\omega}$ photoproduction cross sections. Various versions of pseudoelastic mechanisms are studied and it is shown that although they correctly predict the large $\ensuremath{\rho}:\ensuremath{\omega}$ production ratio, they cannot account for the extremely small preliminary cross section for $\ensuremath{\phi}$ production. It is shown that no combination of one-pion exchange and the diffraction mechanism with exact or broken $\mathrm{SU}(3)$ can explain the low $\ensuremath{\phi}$ production rate. The multiperipheral model may explain the low $\ensuremath{\phi}$ production, but predicts the wrong $\ensuremath{\rho}:\ensuremath{\omega}$ production ratio. Various possible sources of this discrepancy are studied and experimental tests are discussed which can distinguish between the different proposed theories. A large number of new predictions based on exact or broken $\mathrm{SU}(3)$ symmetry are derived and compared with experiment.

Photoproduction of vector mesons as virtual vector meson-proton scattering

Photoproduction of vector mesons as virtual vector meson-proton scattering

A remark on the photoproduction of vector mesons

The cross sections for photoproduction of vector mesons are calculated combining photo-dissociation model and quark model.

High-energy photoproduction of vector mesons and Regge poles

High-energy photoproduction of vector mesons and Regge poles

Photoproduction of vector mesons from nucleons

The photoproduction of ϱ- and ω-mesons from nucleons is treated phenomenologically, emphasizing the suitability of choosing a particular set of 12 invariant amplitudes of this process. These are obtained in analogy with Compton scattering from nucleons so that the expressions for the physical observables are closely related in the two cases. Contributions to the amplitudes from nucleon exchange in the direct channel and one-pion exchange in the crossed channel are given, and the latter diagram is explicitly compared with the few experimental data available at present.

Photoproduction of vector mesons

The amplitude for photoproduction of vector mesons is studied using the approach of dispersion theory. The contribution to the amplitude from the nearest singularities is estimated and numerical results for total and angular distributions of the ω meson are discussed.

Influence of absorption on peripheral photoproduction of vector mesons

Photoproduction ofρ andω mesons on nucleons is considered in the peripheral model. The interaction mechanism is assumed to be pseudoscalar and scalar exchange. Absorptive final-state interactions are taken into account. The differential cross section and the angular distribution for the decay are calculated and compared with experimental data.

Spin Correlations in the Photoproduction of Vector Mesons

Spin correlations are analyzed for the photoproduction of ${1}^{\ensuremath{-}}$ resonances by polarized photons on unpolarized nucleons. The spin of the vector meson can be studied through its decay. Aside from an over-all phase, there are 23 real numbers which comprise the 12 amplitudes specifying the production process. It is found that all but one of these can be determined from measurements with an unpolarized target.