Measurement of Longitudinal Spin Transfer to Lambda Hyperons in Deep-Inelastic Lepton Scattering

TL;DR

This study measures the longitudinal spin transfer to Lambda hyperons in deep-inelastic scattering, providing the most precise data to date and testing models of hyperon spin structure and helicity conservation.

Contribution

It presents the most precise measurement of spin transfer to Lambda hyperons in deep-inelastic scattering, informing models of hyperon spin content and fragmentation.

Findings

Spin transfer value is 0.11 +/- 0.17 (stat) +/- 0.03 (sys)

Results are consistent with helicity conservation in fragmentation

Data agrees with various Lambda spin structure models

Abstract

Spin transfer in deep-inelastic Lambda electroproduction has been studied with the HERMES detector using the 27.6 GeV polarized positron beam in the HERA storage ring. For an average fractional energy transfer <z> = 0.45, the longitudinal spin transfer from the virtual photon to the Lambda has been extracted. The spin transfer along the Lambda momentum direction is found to be 0.11 +/- 0.17 (stat) +/- 0.03 (sys); similar values are found for other possible choices for the longitudinal spin direction of the Lambda. This result is the most precise value obtained to date from deep-inelastic scattering with charged lepton beams, and is sensitive to polarized up quark fragmentation to hyperon states. The experimental result is found to be in general agreement with various models of the Lambda spin content, and is consistent with the assumption of helicity conservation in the fragmentation process.