1. Nuclear Physics Seminar

    "Status of W Boson Production Measurements at PHENIX"

    Presented by Mikhail Stepanov, UMass Amherst

    Tuesday, May 28, 2013, 11 am
    Small Seminar Room, Bldg. 510

    Hosted by: Oleg Eyser

    The measurement of $W^{\pm}$ production in polarized proton-proton collisions at RHIC is an important probe of the proton's polarized sea quark distributions which are poorly constrained at present compared to the valence quarks distributions. Parity-violating single-spin asymmetries, $A_{L}$, measured in $W^{\pm}$ production in longitudinally polarized $p+p$ collisions provide access to the flavor-separated light quark and anti-quark polarized parton distribution functions. The PHENIX experiment observes $W^{\pm}$ through their leptonic decay to $e^{\pm}$ at mid-rapidity ($|\eta|<0.35|$) and to $\mu^{\pm}$ at forward/backward rapidities ($1.2<|\eta|<2.2$). These complementary measurements give access to the sea quark polarizations over different ranges in partonic momentum of a quark/antiquark. In succession to the first measurements performed in 2009 (mid-rapidity) and in 2011 (forward/backward rapidities), in 2012 PHENIX recorded data at $\sqrt{s}$ = 510 GeV with an integrated luminosity of $\approx $50 pb$^{-1}$ which is about twice the size of previous data sets and also takes an advantage of improved beam polarization ($P\approx$ 55$\%$). The parity-violating single-spin asymmetries for $W$ production from the 2012 dataset will be presented; as well as, details and status of the recent analyses and future prospects will be reported.