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arXiv · 2305.10359

Measurement of transverse single-spin asymmetries for dijet production in polarized proton-proton collisions at $\mathbf{\sqrt{s}}$ = 200 $\mathbf{\mathrm{GeV}}$

STAR Collaboration
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Abstract

We report a new measurement of transverse single-spin asymmetries for dijet production in collisions of polarized protons at $\sqrt{s}$ = 200 $\mathrm{GeV}$. Correlations between the proton spin and the transverse momenta of its partons, each perpendicular to the proton momentum direction, are probed at high $Q^2$ $\approx $160 $\mathrm{GeV}^2$. Evidence for nonzero Sivers effects is measured for the first time in dijets from proton-proton collisions, but only when the jets are sorted by their net charge, which enhances the otherwise canceling opposite-sign $u$- or $d$-quark contributions to separate data samples. The resulting asymmetries are compared to recent theoretical calculations. Separately, the associated Sivers observable $\langle k_T \rangle$, the average parton transverse momentum, is extracted using a simple kinematics approach which further enables a determination of the individual partonic contributions to the observed asymmetries.

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STAR Collaboration. 2023-05-17. Measurement of transverse single-spin asymmetries for dijet production in polarized proton-proton collisions at $\mathbf{\sqrt{s}}$ = 200 $\mathbf{\mathrm{GeV}}$. https://doi.org/10.1103/dd1f-hvj2

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