Evidence for spin one resonance production in the reaction gamma gamma* ---> pi+ pi- pi0 pi0

Using data from the TPC/Two-Gamma experiment at the SLAC e + e − storage ring PEP, a C = +1 resonance has been observed in the π + p − p 0 g final state resulting from the fusion of one nearly real and one quite virtual photon. The actual decay channel is probably π + p − p 0 p 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 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 π + p − p 0 p 0 and the γγ coupling makes it unlikely that this state is the mostly ss f 1 (1510), its interpretation may lie outside of conventional meson spectroscopy