Photoproduction of the f1(1285)/η(1295) Mesons using CLAS at Jefferson Lab

This work presents the results of analysis of a meson of mass mx = 1281.0 ± 0.8 MeV/c and a FWHM of Γx = 18.4 ± 1.4 MeV/c seen in CLAS at Jefferson Lab in photoproduction off the proton, γp → xp. The f1(1285), η(1295) or both are candidates for this observed state. Neither of these states has previously been observed in photoproduction. The meson was measured in the decay modes x → ηπ+π−, K+K̄0π−, K−K0π+, and ργ through detection of its charged decay products and the recoil proton. Differential cross sections were obtained via the x → ηπ+π−, K+K̄0π−, and K−K0π+ decay channels from threshold up to a center-of-mass energy of 2.8 GeV, and compared to recent Regge model predictions. Dalitz analysis showed strong evidence for the f1(1285) identity, with the dominance of ηπ+π− decays via a0 (980)π ∓ intermediate state and with interference consistent with a spin one particle. The relative branching fractions Γ(KK̄π)/Γ(ηππ) and Γ(ργ)/Γ(ηππ) were measured, with agreement to world data for the f1(1285) in the former and lower than the world average for the latter.