engleski

Measurement of transverse single-spin asymmetries for dijet production in proton-proton collisions at root s=200 GeV

We report the first measurement of the opening angle distribution between pairs of jets produced in high-energy collisions of transversely polarized protons. The measurement probes (Sivers) correlations between the transverse spin orientation of a proton and the transverse momentum directions of its partons. With both beams polarized, the wide pseudorapidity ($-1 \leq \eta \leq +2$) coverage for jets permits separation of Sivers functions for the valence and sea regions. The resulting asymmetries are all consistent with zero and considerably smaller than Sivers effects observed in semi-inclusive deep inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the new results with the sizable transverse spin effects seen in SIDIS and forward hadron production in pp collisions.

p p; colliding beams polarized beam; transverse jet; pair production angular distribution; (2jet) spin; asymmetry Sivers function p; spin parton; transverse momentum correlation quark; valence quark; sea hadron; hadroproduction small-angle magnetic detector; STAR experimental results Brookhaven RHIC Coll 200 GeV-cms

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