In a parton-model, the cross section for the Drell-Yan processes is given by the following equation.

The asymmetry for the longitudinal spin polarization is given by the following euqation,

, where

Therefore, the measurement of the longitudinal spin asymmetry of the Drell-Yan process will provide information about the helicity distributions of quarks and antiquarks in nucleon.

References

- S. Drell and T.M.Yan, Phys. Rev. Lett. 25 316 (1970).
- F.E. Close et al., Phys. Rev. Lett. 39 1116 (1977)
- G. Moreno et al., Phys. Rev. D43 2815 (1991).
- P.L.McGaughy et al., Phys. Rev. D50 3038 (1994).
- The PHENIX/Spin Collaboration, "Spin Structure Function Physics
with an Upgraded PHENIX Muon Spectrometer, 1994 (unpublished).

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