Evidence for spin-one resonance production in the reaction [gamma][gamma][sup *][r arrow][pi][sup +][pi][sup [minus]][pi][sup 0][pi][sup 0]

Using data from the TPC/Two-Gamma experiment at the SLAC [ital e][sup +][ital e[minus]] storage ring PEP, a [ital C]=+1 resonance has been observed in the [ pi][sup +][ pi][sup [minus]][ pi][sup 0][gamma] final state resulting from the fusion of one nearly real and one quite virtual photon. The actual decay channel is probably [ pi][sup +][ pi][sup [minus]][ pi][sup 0][ pi][sup 0], where one final-state photon is not detected, and the mass of the fully reconstructed state would be approximately 1525 MeV. A four-pion decay mode in turn implies that the resonance has even isospin. The nonobservation of this [ital R](1525) when both initial-state photons are nearly real suggests a spin-1 assignment. Since the large measured value of the product of the branching ratio into [ pi][sup +][ pi][sup [minus]][ pi][sup 0][ pi][sup 0] and the [gamma][gamma] coupling makes it unlikely that this state is the mostly [ital [bar s]s] [ital f][sub 1](1510), its interpretation may lie outside of conventional meson spectroscopy. There is a second, less-significant enhancement observed in the same reaction at a four-pion mass centered around 2020 MeV.