First Measurements of the Double-Polarization Observables $F$, $P$, and $H$ in $\omega$ Photoproduction off Transversely Polarized Protons in the $N^{*}$ Resonance Region

First measurements of double-polarization observables in $\omega$ photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry $F$ has been measured using circularly polarized, tagged photons in the energy range 1200–2700 MeV, and the beam-target asymmetries $H$ and $P$ have been measured using linearly polarized, tagged photons in the energy range 1200–2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon ($N^{*}$) resonances. In particular, contributions from new $N^{*}$ resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum.

Figure 1

Typical examples of signal and background mass distributions from butanol data after applying all kinematic cuts and corrections. The invariant ${\pi }^{+}{\pi }^{-}{\pi }^0$ masses are shown for two energies at the same angle, $0.2<\cos {\mathrm{\Theta }}_{\mathrm{c}.\mathrm{m}.}^{\omega }<0.4$. The black line shows the unweighted distribution from the butanol target, the blue-shaded area shows the background mass distribution (weighted by $1-Q$), and the red line shows the signal distribution (weighted by $Q$).

Figure 2

First-time measurement of the beam-target asymmetry $F$ in $\overrightarrow{\gamma }\overrightarrow{p}\to p\omega$. Shown are distributions in 100-MeV-wide incident-photon energy bins (labeled as $E_{\gamma }[W]$) as a function of $\cos {\mathrm{\Theta }}_{\mathrm{c}.\mathrm{m}.}^{\omega }$ in the center-of-mass frame. Each data point has been assigned its statistical uncertainty, whereas the gray band at the bottom of each panel represents the absolute systematic uncertainties due to the background subtraction. The blue and red solid curves show the BnGa PWA solution and fits by Wei et al. [15], respectively. The blue dashed curve denotes an earlier BnGa solution [16].

Figure 3

First-time measurements of the beam-target asymmetries $H$ (top) and $P$ (bottom) in $\omega$ photoproduction off the proton. Shown are eight 100-MeV-wide energy bins (labeled as $E_{\gamma }[W]$) as a function of $\cos {\mathrm{\Theta }}_{\mathrm{c}.\mathrm{m}.}^{\omega }$ in the center-of-mass frame. Each data point has been assigned its statistical uncertainty, whereas the gray band at the bottom of each panel represents the absolute systematic uncertainties due to the background subtraction. The blue and red solid curves show the BnGa PWA solution and fits by Wei et al. [15], respectively. The blue dashed curve denotes an earlier BnGa solution [16].