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

Le résumé fourni par la source

We present midrapidity measurements from the PHENIX experiment of large parity-violating single-spin asymmetries of high transverse momentum electrons and positrons from ${\mathrm{W}}^{\ifmmode\pm\else\textpm\fi{}}/\mathrm{Z}$ 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 antiquark polarized parton distribution functions due to the parity-violating nature of the $\mathrm{W}$-boson coupling to quarks and antiquarks. The results presented are based on data collected in 2011, 2012, and 2013 with an integrated luminosity of $240\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$, which exceeds previous PHENIX published results by a factor of more than 27. These high ${Q}^{2}$ 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 ${M}_{\mathrm{W}}/\sqrt{s}=0.16$.

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