Components of polarization-transfer to a bound proton in a deuteron measured by quasi-elastic electron scattering

TL;DR

This study measures the polarization transfer components to a bound proton in deuterium via quasi-elastic electron scattering, revealing discrepancies with theoretical models and suggesting an incomplete understanding of the nuclear reaction mechanism.

Contribution

First measurements of all polarization transfer components to a bound proton in deuterium across various missing momenta, with improved precision and comparison to advanced theoretical calculations.

Findings

Good agreement in $P_{x}/P_{z}$ ratios between data and theory

Deviations observed in individual polarization components

Results challenge existing models of nuclear reaction mechanisms

Abstract

We report the first measurements of the transverse ($P_{x}$ and $P_{y}$) and longitudinal ($P_{z}$) components of the polarization transfer to a bound proton in the deuteron via the $^{2}\mathrm{H}(\vec{e},e'\vec{p})$ reaction, over a wide range of missing momentum. A precise determination of the electron beam polarization reduces the systematic uncertainties on the individual components, to a level that enables a detailed comparison to a state-of-the-art calculation of the deuteron that uses free-proton electromagnetic form factors. We observe very good agreement between the measured and the calculated $P_{x}/P_{z}$ ratios, but deviations of the individual components. Our results cannot be explained by medium modified electromagnetic form factors. They point to an incomplete description of the nuclear reaction mechanism in the calculation.