Recent STAR results and prospects of $W^{-(+)}$ boson production in polarized $\vec{p}+\vec{p}$ collisions at RHIC

Abstract

In 2009, the RHIC spin physics program completed the first data taking period of polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=500$ GeV, accumulating ~12 pb${}^{-1}$ with ~39% beam polarization. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. $W^{-(+)}$ bosons are produced in $\bar{u}+d(\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^{-}+\overline{{\nu }_e}(e^{+}+{\nu }_e)$, where only the respective charged lepton is measured. The discrimination of $\bar{u}+d$ and $\bar{d}+u$ quark combinations requires distinguishing the charge sign of high $p_T$ electrons and positrons, which in turn requires precise tracking information. At mid-rapidity, STAR relies on the Time Projection Chamber. At forward rapidity, new tracking capabilities will be provided by the Forward GEM Tracker, consisting of six triple-GEM detectors which are under construction. The suppression of QCD background over W boson signal events by several orders of magnitude is accomplished by using the highly segmented STAR Electromagnetic Calorimeters to impose isolation criteria suppressing jet events, and vetoing dijet events based on the measured away side energy. The status of the STAR results on the first measurements of the cross section and single spin asymmetry for $W^{-(+)}$ boson production in polarized $\vec{p}+\vec{p}$ collisions will be presented along with a discussion of prospects involving the STAR Forward GEM Tracker.

5 pages, 4 figures, Proceedings of SPIN2010 international symposium, Julich, Germany, September 27 - October 2, 2010

References in corpus (4)

• Extraction of Spin-Dependent Parton Densities and Their Uncertainties
• Quark helicity distributions in the nucleon for up, down, and strange quarks from semi--inclusive deep--inelastic scattering
• Longitudinal double-spin asymmetry and cross section for inclusive jet production in polarized proton collisions at sqrt(s) = 200 GeV
• Single-spin asymmetries with weak bosons at RHIC