Measurement of Sivers Asymmetries for Di‐jets in $s = 200 GeV$ pp Collisions at STAR Available to Purchase

Measurement of the transverse spin dependence of the di‐jet opening angle in pp collisions at $s = 200 GeV$ 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.