Journal Article Measurement of parity-violating spin asymmetries in W± production at midrapidity in longitudinally polarized p+p collisions

PHENIX Collaboration  ,  Chujo, T.  ,  Esumi, S.  ,  Miake, Y.

93 ( 5 )  , p.051103 , 2016-03 , American Physical Society
We present midrapidity measurements from the PHENIX experiment of large parity-violating single-spin asymmetries of high transverse momentum electrons and positrons from W±/Z decays, produced in longitudinally polarized p+p collisions at center of mass energies of s√=500 and 510 GeV. These asymmetries allow direct access to the antiquark polarized parton distribution functions due to the parity-violating nature of the W-boson coupling to quarks and antiquarks. The results presented are based on data collected in 2011, 2012, and 2013 with an integrated luminosity of 240  pb−1, which exceeds previous PHENIX published results by a factor of more than 27. These high Q2 data probe the parton structure of the proton at W mass scale and provide an important addition to our understanding of the antiquark parton helicity distribution functions at an intermediate Bjorken x value of roughly MW/s√=0.16

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