Abstract
The production of [Formula: see text] bosons in longitudinally polarized [Formula: see text] collisions is a powerful tool to study the spin-flavor structure of the proton. We report measurements of single- and double-spin asymmetries for [Formula: see text] and [Formula: see text] production in longitudinally polarized proton-proton collisions at [Formula: see text] GeV at RHIC. The single-spin asymmetry results for [Formula: see text] from data sets collected by STAR experiment in 2011 and 2012 provided new constraints on proton’s polarized sea quark distributions and prefer a sizable value for [Formula: see text] polarization. The status for the analysis of a much larger data set collected by STAR in 2013 will also be given.
Highlights
Understanding the spin structure of proton is a fundamental and longstanding challenge in nuclear physics
The flavor separated contribution can be accessed through semi-inclusive deep-inelastic scattering (DIS) experiments, but they have to rely on the use of fragmentation functions to relate the measurements of the final state hadrons to the quark and anti-quark distributions
We report the results for the single- and double-spin asymmetries for W ± and Z/γ∗
Summary
Understanding the spin structure of proton is a fundamental and longstanding challenge in nuclear physics. The coupling of W ± bosons to left-handed quarks and right-handed This is an Open Access article published by World Scientific Publishing Company. Zhang anti-quarks determines the helicity of the incident quarks This provides a theoretically clean probe of the helicity-dependent PDFs through a parity-violating longitudinal single-spin asymmetry, which is defined as AL = (σ+ − σ−)/(σ+ + σ−), where σ+(−) is the cross section when the polarized beam has positive (negative) helicity. First measurements of the single-spin asymmetry, AL, for W production at RHIC were reported by the STAR5 and PHENIX6 c√ollaborations from a data set collected in 2009, the successful commission run at s=500GeV. Production measured from data sets collected in 2011 and 2012 by STAR experiment, with integrated luminosity of 9 and 77 pb−1, and average beam polarization of 49% and 56%, respectively
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