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

Adare, A. and Aidala, C. and Ajitanand, N. N. and Akiba, Y. and Akimoto, R. and Csanád, Máté and Csörgő, Tamás and Imrek, József and Varga-Kőfaragó, Mónika and Nagy, Márton and Novák, Tamás and Ster, András and Sziklai, János István and Vargyas, Márton and Vértesi, Róbert (2016) Measurement of parity-violating spin asymmetries in W± production at midrapidity in longitudinally polarized p+p collisions. PHYSICAL REVIEW D, 93. ISSN 2470-0010

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Abstract

We present measurements from the PHENIX experiment of large parity-violating single spin asymmetries of high transverse momentum electrons and positrons from $W^\pm/Z$ decays, produced in longitudinally polarized $p$$+$$p$ collisions at center of mass energies of $\sqrt{s}$=500 and 510~GeV. These asymmetries allow direct access to the anti-quark polarized parton distribution functions due to the parity-violating nature of the $W$-boson coupling to quarks and anti-quarks. 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 $Q^2$ data provide an important addition to our understanding of anti-quark parton helicity distribution functions.

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