Measurement of the helicity asymmetry $E$ in $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ photoproduction

Abstract

The double-polarization observable $E$ was studied for the reaction $\gamma p\to p\omega$ using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally-polarized frozen-spin target (FROST). The observable was measured from the charged decay mode of the meson, $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$, using a circularly-polarized tagged-photon beam with energies ranging from the $\omega$ threshold at 1.1 to 2.3 GeV. A partial-wave analysis within the Bonn-Gatchina framework found dominant contributions from the $3/2^{+}$ partial wave near threshold, which is identified with the sub-threshold $N(1720)3/2^{+}$ nucleon resonance. To describe the entire data set, which consisted of $\omega$ differential cross sections and a large variety of polarization observables, further contributions from other nucleon resonances were found to be necessary. With respect to non-resonant mechanisms, $\pi$ exchange in the $t$-channel was found to remain small across the analyzed energy range, while pomeron $t$-channel exchange gradually grew from the reaction threshold to dominate all other contributions above $W\approx 2$ GeV.

arXiv comment12 pages, 8 figures

References in corpus (20)

• Baryon spectroscopy
• Progress Toward Understanding Baryon Resonances
• Exclusive vector meson production at HERA
• Differential cross sections and spin density matrix elements for the reaction gamma p -> p omega
• Measurement of the beam asymmetry $\Sigma$ for ${\pi }^0$ and $\eta$ photoproduction on the proton at $E_{\gamma }=9$ GeV
• Photoproduction of the $\omega$ meson off the proton near threshold
• The Jefferson Lab Frozen Spin Target
• Nucleonic resonance excitations with linearly polarized photon in $\gamma p\to \omega p$
• Partial wave analysis of the reaction gamma p -> p omega$ and the search for nucleon resonances
• First measurement of the helicity asymmetry $E$ in $\eta$ photoproduction on the proton
• Photoproduction of ω Mesons off the Proton
• First Measurement of the Polarization Observable E in the $\vec{p}(\vec{\gamma },{\pi }^{+})n$ Reaction up to 2.25 GeV
• Multivariate side-band subtraction using probabilistic event weights
• Systematic Regge theory analysis of omega photoproduction
• $N^{\ast }$ decays to $N\omega$ from new data on $\gamma p\to \omega p$
• Beam asymmetry in near threshold omega photoproduction off the proton
• Measurement of double polarisation asymmetries in $\omega$-photoproduction
• The photoproduction of vector mesons
• 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 Σ beam asymmetry for the ω photo-production off the proton and the neutron at GRAAL

Cited by in corpus (9)

• Polarized ultrashort brilliant multi-GeV $\gamma$-rays via single-shot laser-electron interaction
• Light Baryon Spectroscopy
• Photoproduction Reactions and Non-Strange Baryon Spectroscopy
• Electron spin- and photon polarization-resolved probabilities of strong-field QED processes
• Nucleon resonances in $\gamma p\to \omega p$ reaction
• 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
• Differential cross section and photon beam asymmetry for the gamma p -> pi+ n reaction at forward pi+ angles at Egamma=1.5-2.95 GeV
• First Measurements of the Double-Polarization Observables $F$, $P$, and $H$ in $\omega$ Photoproduction off Transversely Polarized Protons in the $N^{\ast }$ Resonance Region
• Intrinsic Nonlocality of Spin- and Polarization-Resolved Probabilities in Strong-Field Quantum Electrodynamics