First Measurement of Transferred Polarization in the Exclusive e p --> e' K+ Lambda Reaction

TL;DR

This study reports the first measurement of transferred polarization in the exclusive ep --> e'K+ Lambda reaction, providing new insights into hyperon production mechanisms and resonance contributions at Jefferson Lab.

Contribution

It presents the inaugural measurement of transferred polarization in this reaction, offering data that tests and constrains hadrodynamic models and quark-pair creation theories.

Findings

Hyperon polarization is sensitive to resonance contributions.

Quark pair spins are predominantly anti-aligned.

Results support specific quark-pair creation models.

Abstract

The first measurements of the transferred polarization for the exclusive ep --> e'K+ Lambda reaction have been performed in Hall B at the Thomas Jefferson National Accelerator Facility using the CLAS spectrometer. A 2.567 GeV electron beam was used to measure the hyperon polarization over a range of Q2 from 0.3 to 1.5 (GeV/c)2, W from 1.6 to 2.15 GeV, and over the full center-of-mass angular range of the K+ meson. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A non-relativistic quark model interpretation of our data suggests that the s-sbar quark pair is produced with spins predominantly anti-aligned. Implications for the validity of the widely used 3P0 quark-pair creation operator are discussed.