Recent results of gluon and sea quark polarization measurements in polarized proton-proton collisions at STAR

Abstract

The STAR experiment at RHIC is carrying out a comprehensive high-energy spin physics program to understand the internal structure and dynamics of the proton in polarized proton-proton collisions at $\sqrt{s}=200$ GeV and $\sqrt{s}=500/510$ GeV. STAR has the capability, with nearly full azimuthal coverage, to reconstruct leptons, hadrons and jets in the mid-rapidity region ($|\eta |<1$). The results for inclusive jet longitudinal double spin asymmetries taken during the 2009 RHIC run indicate the first non-zero gluon contribution ($\Delta g(x,Q^2)/g(x,Q^2)$) to the proton spin for $0.05<x<1$ (Bjorken-x: momentum fraction of partons). Recent longitudinal single-spin asymmetry measurements of $W^{+/-}$ bosons at $\sqrt{s}=500/510$ GeV in polarized proton-proton collisions provide a direct probe of the polarized anti-u and anti-d quark distributions ($\Delta \bar{u}(x,Q^2)$, $\Delta \bar{d}(x,Q^2)$). These results better constrain the polarized gluon and sea quark distributions of the proton in the RHIC sensitive kinematic region. Future measurements with continuing high energy polarized proton-proton run at RHIC and detector upgrade will explore the gluonic contribution to the proton spin in extended range.

arXiv comment8 pages, 9 figures. Invited talk presented at the 30th Winter Workshop on Nuclear Dynamics (WWND 2014), Galveston, Texas, USA, April 6-12, 2014. To be published in Journal of Physics: Conference Series (JPCS). The author may be contacted via: [email protected]

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