Measurement of the Single Spin Asymmetry in W Boson Production in Polarized p+p collisions at sqrt{s} = 510 GeV with the PHENIX Muon Spectrometer

Abstract

Measurement of parity violating single spin asymmetry of W boson production in polarized p+p collisions provides clean access to the polarized antiquark parton distribution functions (PDF) in order to understand the spin structure of the proton. The asymmetry for W±/Z \rightarrow \mu^{±} has been measured using longitudinally polarized proton proton collisions at ps = 510 GeV at RHIC using the PHENIX muon spectrometer. The PHENIX muon detector measures muons from W/Z decays, and it covers pseudorapidity region of 1.2 <

\eta

< 2.4. The data analyzed in this thesis was collected in 2012 with total integrated luminosity of 53 pb^{−1}. The resulting asymmetries are:

A^{\mu^{-}}_{L} = 0.706 +0.439 −0.345 (stat.) +0.294 −0.450(syst.), <\eta >= 1.75 (68% C.L) A^{\mu^{-}}_{L} = −0.130 +0.338 −0.359 (stat.) +0.421 −0.566(syst.), <\eta >= −1.75 (68% C.L) A^{\mu^{+}}_{L} = 0.079 +0.203 −0.200 (stat.) +0.209 −0.226(syst.), <\eta >= 1.71 (68% C.L) A^{\mu^{+}}_{L} = 0.122 +0.200 −0.199 (stat.) +0.218 −0.178(syst.), <\eta >= −1.71 (68% C.L)

and they are consistent with the theoretical predictions from the next-leading-order global analyses within 1 sigma uncertainty, except for the asymmetry for \mu^{+} which is 1.5 sigma away to the upper direction. This results will improve the constraints on the light antiquark PDFs in the future global analysis.