Exclusive production of pp¯π+π- in photon-photon collisions

We report a measurement of the e+e-→e+e-pp¯π+π- process with the TPC/Two-Gamma facility at the PEP e+e- storage ring at SLAC. Forty-five pp¯π+π- events were identified in data corresponding to an integrated e+e- luminosity of 142 pb-1. The cross section for γγ→pp¯π+π- is given both as a function of the γγ center-of-mass energy Wγγ, with Wγγ between 2.5 and 5.5 GeV, and as a function of the in variant mass squared q2 of one of the photons, with -q2<7 GeV2. This cross section falls much less rapidly with Wγγ than does the cross section for a similar process, γγ→pp¯. No Δ0Δ¯0 production is observed, and only a small fraction of the events at low Wγγ is consistent with γγ→Δ++Δ¯--, Δ++p¯π-, or Δ¯--pπ+. In an expanded search through the same data, four events compatible with either ΛΛ¯(Λ→pπ-) or Σ0Λ¯(Σ0→Λγ) production were found.