Exclusive production of p bar pπ+π- in photon-photon collisions

We report a measurement of the e+e-→e+e-p bar pπ+π- process with the TPC/Two-Gamma facility at the PEP e+e- storage ring at SLAC. Forty-five p bar pπ+π- events were identified in data corresponding to an integrated e+e- luminosity of 142 pb-1. The cross section for γγ→p bar pπ+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 invariant 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→p bar p. No Δ0 bar Δ 0 production is observed, and only a small fraction of the events at low Wγγ is consistent with γγ→Δ++bar Δ --, Δ++bar pπ-, or bar Δ --pπ+. In an expanded search through the same data, four events compatible with either Λ bar Λ (Λ→pπ-) or Σ0 bar Λ (Σ0→Λγ) production were found