Background Sources

One of the main challenges in the measurement of this rare $\gamma \gamma n$ process is to account for the intense source of single photons and photon-pairs from the dominant processes

$$\pi^{-} + p \rightarrow \pi^{0} + n \;\; (60.7\%),$$ (5.3)

$$\hookrightarrow \gamma + \gamma \;\; (k \sim 55-83 \; {\rm MeV}),$$

$$\pi^{-} + p \rightarrow \gamma + n \;\; (39.3\%, k \sim 129 \; {\rm MeV}).$$ (5.4)

in addition to several other potentially large background sources. In Section 5.3, we describe the various sources of background, and steps taken to eliminate them.