Electron Beam Single-Spin Asymmetries in the Resonance Region with Final Hadrons Observed

TL;DR

This paper investigates single-spin asymmetries in electron-proton inelastic scattering within the resonance region, highlighting how observing final state hadrons like pions reveals asymmetries suppressed in simpler cases.

Contribution

It provides the first detailed analysis of beam-transverse and normal single-spin asymmetries involving observed pions in the resonance region, emphasizing the role of final state interactions.

Findings

Asymmetries of order tens of ppm when both electron and pion are observed.

Asymmetries of order one ppm when only the pion is observed.

No asymmetry with single-photon exchange if only the observed particle is considered.

Abstract

We study beam-transverse and normal single-spin asymmetry for electron-proton inelastic scattering in the resonance region for the case where a pion is observed in the final state. There is no beam single-spin asymmetry if the observed particle has single-photon exchange as its only interaction, but this is naturally circumvented when one observes a strongly interacting final state particle. The asymmetries are not large as there is an electron mass divided by momentum transfer suppression. We present results for the cases where the final electron and a pion are both observed, with asymmetries of order tens of ppm, and where only a final pion is observed, with asymmetries of order one ppm.