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

TL;DR

This paper investigates backward meson production in electron-proton collisions at an electron-ion collider, highlighting its similarity to baryon stopping and providing cross section estimates for experimental feasibility.

Contribution

It introduces a theoretical framework for backward meson production at high energies and compares it to baryon stopping, proposing experimental approaches at an electron-ion collider.

Findings

Backward $ ext{omega}$ production rate is about 1/300 of forward production.

Backward production involves large momentum transfer near the kinematic limit.

The study discusses detector requirements for observing backward mesons.

Abstract

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. We then explore how backward production can be explored at higher energies than are available at fixed target experiments, by studying production at an electron-ion collider. We calculate the expected $ep$ cross sections and rates, finding that the rate for backward $\omega$ production is about 1/300 that of forward $\omega$s. We discuss the kinematics of backward production and consider the detector requirements for experimental study.