Sea Quark Polarization Measurement Via W‐Boson in Forward Rapidity at PHENIX

The Relativistic Heavy Ion Collider (RHIC) at BNL provides a unique opportunity to collide polarized protons. One of the hightlight of the spin program at root s = 500 GeV is the direct measurement of sea quark contribution to the proton spin via W-boson production by measuring parity violating single spin asymmetry. A new trigger on forward muons in PHENIX identiinAes and triggers on high momentum Ws suppressing a large number of low momentum muons coming from hadronic decays. Since the original muon trigger will fire on any muon above similar to 2 GeV/c, it will not provide the required rejection factor for 500 GeV running, which is about 4500. New fast readout trigger electronics and timing device were developed and installed to existing muon detection system in PHENIX. The performance of the new muon trigger and the fast turnaround offline analysis result from the first root s = 500 GeV production run (Run11) will be discussed.