Measurement of transverse single-spin asymmetries for dijet production in polarized proton-proton collisions at √s = 200 GeV
- We report a new measurement of transverse single-spin asymmetries for dijet production in collisions of polarized protons at s√ = 200 GeV. Correlations between the proton spin and the transverse momenta of its partons, each perpendicular to the proton momentum direction, are probed at high Q2 ≈160 GeV2. The associated Sivers observable ⟨kT⟩, the average parton transverse momentum, is extracted using simple kinematics. Nonzero Sivers effects are observed for the first time in dijets from proton-proton collisions, but only when the jets are sorted by their net charge, which enhances the u- or d-quark contributions to separate data samples. This also enables a simple kinematic approach for determination of the individual partonic contributions to the observed asymmetries.