Backward-Angle ($u$-channel) Production at an Electron-Ion Collider

Understand

In backward photoproduction of mesons, $\gamma p\rightarrow M p$, the target proton takes most of the photon momentum, while the produced meson recoils in the direction from which the photon came.

• Thus the Mandelstam $u$ is small, while the squared momentum transfer $t$ is typically large, near the kinematic limit.
• In a collider geometry, backward production transfers the struck baryon by many units of rapidity, in a striking similarity to baryon stopping.
• We explore this similarity, and point out the similarities between the Regge theories used to model baryon stopping with those that are used for backward production.