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The gauge invariant definition of the Sivers function predicts the opposite sign for the Sivers function in SIDIS compared to processes with color charges in the initial state and a colorless final state such at Drell-Yan and W/Z boson production. In W/Z production, it is guaranteed that an anti-quark is involved as in Drell-Yan process.
We can say: SpinQuest will perform the first measurement of the Sivers asymmetry in Drell-Yan pp scattering from the sea quarks.
SpinQuest will explore properties of the nucleon's spin composition by investigating correlation of the light antiquarks motion relative to the nucleon spin.
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