| The contribution from the sea quarks to the proton spin have been poorly constrained mainly because of the limited knowledge we have on the fragmentation function in polarized Semi Inclusive Deep Inelastic Scattering (SIDIS) experiments. The parity-violating longitudinal single spin asymmetry AL in the production of W bosons in p + p collisions does not involve fragmentation function and is an alternative better way of exploring the polarization of sea quarks in the proton. The measurement will be useful especially in constraining u and d¯ in the very backward and forward rapidities respectively. However, identifying the muons from the decay of the W is challenging due to a great background of hadronic in flight decays and other muon producing processes such as heavy flavor decays. In the forward and backward hemispheres of PHENIX at RHIC, the muon spectrometers have been recently upgraded in order to provide additional trigger and tracking information to suppress those backgrounds. One of those upgrades is the Forward Vertex (FVTX) detector, a silicon-strip tracker. In 2013, PHENIX accumulated the largest amount of polarized p + p collision data ever collected in the world (∼ 240pb--1 ) at s = 510 GeV with a beam polarization of 56%. The analysis techniques used to extract the signal from the data and the longitudinal single spin asymmetries AL in RHIC 2013 run will be discussed. |
