Formation of spin-one mesons by photon-photon fusion

We have observed the formation of two spin-one mesons in γ γ fusion reactions in which one photon was highly virtual. The first, consistent with being the Jpc= 1++ f1(1285), was seen in the final state ηπ+ π- (η γgamma; ) as was 'he η (958). We have previously reported the observation of the second spin-one state, the χ(1420), in the final state K++Ks₀ π The formation of this state, which may be the f1(1420) observed in hadronic interactions, is reanalyzed using a new model and more data. We consider whether the χ(1420) could be the partner of the f1(1285) in the JK=1++ meson nonet. The yy∗ width of each resonance was determined in several Q2 bins. Using a model due to Cahn with a ρ form factor, we obtained for the coupling parameter 1285)) the value 2.4 × 0.5±0.5 keV. We also found B{X( 1420) KK π)Tyy{X{ 1420)) = 1.3±0.5±0.3 keV using a p form factor, or 0.63±0.24±0.15 keV using a <b form factor. The decay distributions of the observed AT.420) events arc consistent with a decay proceeding via K∗{892)K, and favor positive, but do not exclude negative, parity. Assuming that the X(1420) and the f1(1285) are members of the same qq meson nonet and that B{X(1420) ) 1, and using a φ form factor in the model for X(1420) formation, we determined the singlet-octet mixing angle of that nonet. The result, (45.4±6.2)°, agrees well with the 42.2∗ implied by the Gell-Mann-Okubo quadratic mass formula; it is farther from the 35.3° ideal mixing angle. Our results are consistent wiih the X (1420) being the mostly ss isoscalar member of the axial-vector qq meson nonet; however, we have no evidence contrary to hypotheses that the 1420) is an exotic q2q 2 or qqg slate.