Exclusive production of $p\overline{p}{\pi }^{+}{\pi }^{-}$ in photon-photon collisions

We report a measurement of the $e^{+}{e}^{-}\to e^{+}{e}^{-}p\overline{p}{\pi }^{+}{\pi }^{-}$ process with the TPC/Two-Gamma facility at the PEP $e^{+}{e}^{-}$ storage ring at SLAC. Forty-five $p\overline{p}{\pi }^{+}{\pi }^{-}$ events were identified in data corresponding to an integrated $e^{+}{e}^{-}$ luminosity of 142 ${\mathrm{pb}}^{-1\mathrm{}}$. The cross section for $\gamma \gamma \to p\overline{p}{\pi }^{+}{\pi }^{-}$ is given both as a function of the $\gamma \gamma$ center-of-mass energy $W_{\gamma \gamma }$, with $W_{\gamma \gamma }$ between 2.5 and 5.5 GeV, and as a function of the in variant mass squared $q^2$ of one of the photons, with $-q^2<7\mathrm{}$ Ge${\mathrm{V}}^2$. This cross section falls much less rapidly with $W_{\gamma \gamma }$ than does the cross section for a similar process, $\gamma \gamma \to p\overline{p}$. No ${\Delta }^0{\overline{\Delta }}^0$ production is observed, and only a small fraction of the events at low $W_{\gamma \gamma }$ is consistent with $\gamma \gamma \to {\Delta }^{++}{\overline{\Delta }}^{--}$, ${\Delta }^{++}\overline{p}{\pi }^{-}$, or ${\overline{\Delta }}^{--}p{\pi }^{+}$. In an expanded search through the same data, four events compatible with either $\Lambda \overline{\Lambda }(\Lambda \to p{\pi }^{-})$ or ${\Sigma }^0\overline{\Lambda }({\Sigma }^0\to \Lambda \gamma )$ production were found.