Single Longitudinal-Spin Asymmetries in Lepton-Pair Production at RHIC and J-PARC

TL;DR

This paper investigates single longitudinal-spin asymmetries in lepton-pair production at RHIC and J-PARC, showing that these asymmetries, arising from one-loop amplitudes, can be significant and serve as tests for perturbative QCD predictions.

Contribution

The study revisits the one-loop calculation of the absorptive part of production amplitudes, demonstrating potential sizable asymmetries at RHIC and J-PARC, and highlights their importance for testing QCD scattering phases.

Findings

Asymmetries can be sizable at RHIC and J-PARC.

Measurement of asymmetries tests one-loop QCD predictions.

Supports study of transverse-spin asymmetries in the same kinematic region.

Abstract

We study the single longitudinal-spin asymmetries in lepton-pair production with large transverse-momentum at RHIC and J-PARC experiments. The asymmetries in the azimuthal angular distribution of a lepton can arise from an absorptive part of production amplitudes. We revisit the one-loop calculation for the absorptive part of production amplitudes in perturbative QCD, and show that the asymmetries can be sizable at RHIC and J-PARC. Measurement of the asymmetries would test the one-loop prediction for the scattering phase of this process, and provide support for a study of the single transverse-spin asymmetries in the same kinematical region.