Measurement of the analysing power in proton-proton elastic scattering at small angles

TL;DR

This study measures the proton analysing power in elastic scattering at small angles across multiple energies, revealing discrepancies with existing models and leading to an improved phase shift analysis.

Contribution

It provides new measurements of proton analysing power at various energies and updates phase shift analysis to better fit the data.

Findings

ANKE data at higher energies exceed existing model predictions

Updated phase shift analysis improves data description

Measurements are consistent across detection methods

Abstract

The proton analysing power in $\vec{p}p$ elastic scattering has been measured at small angles at COSY-ANKE at 796 MeV and five other beam energies between 1.6 and 2.4 GeV using a polarised proton beam. The asymmetries obtained by detecting the fast proton in the ANKE forward detector or the slow recoil proton in a silicon tracking telescope are completely consistent. Although the analysing power results agree well with the many published data at 796 MeV, and also with the most recent partial wave solution at this energy, the ANKE data at the higher energies lie well above the predictions of this solution at small angles. An updated phase shift analysis that uses the ANKE results together with the World data leads to a much better description of these new measurements.