Recent results of high-energy spin phenomena of gluons and sea-quarks in polarized proton-proton collisions at RHIC at BNL

Abstract

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized proton collisions at $\sqrt{s}=200\,$GeV and $\sqrt{s}=500\,$GeV to gain a deeper insight into the spin structure and dynamics of the proton. One of the main objectives of the spin physics program at RHIC is the precise determination of the polarized gluon distribution function. The STAR detector is well suited for the reconstruction of various final states involving jets, $\pi^{0}$, $\pi^{\pm}$, e$^{\pm}$ and $\gamma$, which allows to measure several different processes. Recent results suggest a gluon spin contribution to the proton spin at the same level as the quark spin contribution itself. The production of $W$ bosons in polarized p+p collisions at $\sqrt{s}=500\,$GeV opens a new era in the study of the spin-flavor structure of the proton. $W^{-(+)}$ bosons are produced in $\bar{u}+d\;(\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^{-}+\bar{\nu}_{e}\;(e^{+}+\nu_{e})$, where only the respective charged lepton is measured. Results of $W^{-(+)}$ production suggest a large asymmetry between the polarization of anti-$u$ and anti-$d$ quarks.