Measurement of Differential Cross Sections and Spin Density Matrix Elements along with a Partial Wave Analysis for γp→ pω using CLAS at Jefferson Lab

This work presents measurements of differential cross sections, dσ/d cos θCM , and spin density ma-trix elements,ρMM ′ , for the reaction γp→ pω in the energy range 1.72 GeV<√s <2.84 GeV. Thedata were collected at Jefferson Lab, using the CLAS detector, as part of the g11a run period in2004. OurρMM ′ measurements vastly increase the precision of the world’s data and extend the largeangle measurements by over 400 MeV in√s. Our data confirms that for√s < 2.1 GeV, the forwardangle (small |t|) production amplitude is dominated by t-channel π exchange. At higher energies,existing non-resonant models do a poor job of describing our data. In particular, u-channel modelsfail to reproduce our highest energy backwardsρMM ′ measurements. A mass-independent partial wave analysis has also been performed. Near threshold, the dominantresonance contributions extracted are the **** F15(1680) and *** D13(1700). Together with thet-channel π exchange, these three waves provide a remarkably good description of our differentialcross section and spin density matrix element measurements for√s < 2 GeV. Strong, but notconclusive, evidence for the **** G17(2190) has also been extracted. Improved non-resonant modelsmay be necessary to irrefutably show whether this state contributes to ω photoproduction. Evidencefor missing resonances is suggestive, but inconclusive without theoretical input.