f2(1525) meson production in two-photon reactions

The production of the tensor meson f2'(1525) in two-photon reactions was studied using the TPC/Two-Gamma detector facility at the electron-positron storage ring PEP at a beam energy of 14.5 GeV. The f2'(1525) meson was observed in the untagged (two quasi-real photons) reaction e+e- → e+e-Ks0K20 → e+e-2π+2π- and in the singly-tagged (one quasi-real and one highly virtual photon) reaction e+e- → e+e-K+K-. A measurement of the f2' radiative width was performed in the untagged Ks0ks0 final state under the assumption of helicity-2 for the two-photon state. A value for the tensor meson nonet mixing angle was extracted: ΘT = 24.8 ± 3.8 degree, which implies that the quark content of the f2' (1525) is almost entire s bar s. In the singly-tagged K+K- channel, the helicity structure of the f2'(1525) was studied. It was found to be consistent with 100% helicity-2. Under the assumption of helicity-2, the observed Q2 dependence was found to be in good agreement with a φ-pole form. The observed cross section σ(γγ → K bar K) as a function of the K bar K invariant mass in the two final states Ks0K20 and K+K- agrees very well with the predicted interference pattern among the tensor mesons f2(1270), α20(1320), and f2'(1525). The interference between the f2 and the α20 is destructive in the Ks0Ks0 channel and constructive in the K+K- channel