The Drell-Yan production of lepton pairs has been studied for two decades and regarded as a useful probe of the hadron structure. In this process quark and anti-quark annihilate into massive off-shell photon and the photon decays into lepton pairs. The subprocess has the maximum analyzing power,
Thus the asymmetry for Drell-Yan process is written as
where a denotes the quark flavor, and 
represents electric charge
of flavor a,
and the helicity distribution anti-quark can be determined.
The asymmetry is the weighted sum of the 
and 
assuming strange and other heavy
quark contribution to the
asymmetry is small. The weight for the 
is higher than that for
the 
due to its electric charge and its abundance.
Thus the asymmetry for Drell-Yan production of lepton pairs
will provide an information on the 
polarization which is
contaminated by the 
polarization.