The search for exotic mesons in ηπ^- From photoproduction with CLAS

Over twenty years ago QCD-inspired models of hadronic states suggested the existence of mesons beyond the Naive Quark Model (NQM), which motivated a rigorous search for exotic mesons. The lightest of these states is the π₁(1400) decaying to hp- observed by experiment E852 at Brookhaven [1] and the VES collaboration at IHEP. Photoproduction is predicted to favor production of a J^PC = 1^-+ gluonic excitation resulting in the increase of the ratio of π₁ to a₂ mesons. A Partial Wave Analysis was conducted on the reaction γ p → Δ⁺⁺X → pπ⁺π-(η), using the Δ⁺⁺ to select the pion exchange. The analysis has shown the final spectra of the resonance decaying to ηπ^- to be dominated by the quantum state of J^PC = 2⁺⁺ corresponding to the presence of the a₂(1320). The J^PC = 1^-+ state, shows no structure in the intensity distribution. The phase difference between the J^PC = 1^-+ and J^PC = 2⁺⁺ amplitudes show the interference between the two states. The PWA mass independent fits, along with the mass dependent fits of the partial wave results, will be shown for the ηπ^-.