Measurement of the Σ beam asymmetry for the ω photo-production off the proton and the neutron at GRAAL

Abstract

We report on new measurements of the beam asymmetry for ω photo-production on proton and neutron in Hydrogen and Deuterium targets from the GRAAL collaboration. The beam asymmetry values are extracted from the reaction threshold (E_γ = 1.1 GeV in the free nucleon kinematics) up to 1.5 GeV of incoming photon energy. For the first time both the radiative and the three-pion decay channels are simultaneously investigated on the free proton. Results from the two decay channels are in agreement and provide important constraints for the determination of resonant state contributions to the ω production mechanism. First experimental results on the deuteron allow the extraction of the Σ beam asymmetry on quasi-free nucleons. Comparison of the results for free and quasi-free kinematics on the proton shows a generally reasonable agreement, similar to the findings in pseudo-scalar meson photo-production reactions. For the first time measurements on quasi-free neutrons are available, showing that both the strength and the angular distributions of the beam asymmetry are sensibly different from the results on the proton target.

15 pages, 10 figures and 1 table

References in corpus (7)

• Dynamical coupled-channel model of meson production reactions in the nucleon resonance region
• Measurement of eta photoproduction on the proton from threshold to 1500 MeV
• Differential cross sections and spin density matrix elements for the reaction gamma p -> p omega
• Partial wave analysis of the reaction gamma p -> p omega$ and the search for nucleon resonances
• Beam asymmetry in near threshold omega photoproduction off the proton
• Dynamical coupled channel calculation of pion and omega meson production
• Vacuum pseudoscalar susceptibility

Cited by in corpus (7)

• Light Baryon Spectroscopy
• Measurement of the helicity asymmetry $E$ in $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ photoproduction
• Nucleon resonances in $\gamma p\to \omega p$ reaction
• Photon beam asymmetry $\Sigma$ in the reaction $\vec{\gamma }p\to p\omega$ for $E_{\gamma }$ = 1.152 to 1.876 GeV
• Measurement of the beam asymmetry $\Sigma$ and the target asymmetry $T$ in the photoproduction of $\omega$ mesons off the proton using CLAS at Jefferson Laboratory
• Pomeron, nucleon-resonance, and $(0^{+},0^{-},1^{+})$-meson contributions in $\varphi$-meson photoproduction
• Features of $\omega$ photoproduction off nucleon target at forward angles : Dominance of $\pi$ exchange with Regge cuts and scaling of differential cross sections