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Measurement of Sivers Asymmetries for Di-jets in s=200 GeV pp Collisions at STAR

J. Balewski

hep-exarXiv:hep-ex/0612036

Abstract

Measurement of the transverse spin dependence of the di-jet opening angle in pp collisions at sqrts=200 GeV has been performed by the STAR collaboration. An analyzing power consistent with zero has been observed over a broad range in pseudorapidity sum of the two jets with respect to the polarized beam direction. A non-zero (Sivers) correlation between transverse momentum direction of partons in the initial state and transverse spin orientation of the parent proton has been previously observed in semi-inclusive deep inelastic scattering (SIDIS). The present measurements are much smaller than deduced from predictions made for STAR di-jets based on non-zero quark Sivers functions deduced from SIDIS, and furthermore indicate that gluon Sivers asymmetries are comparably small.

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