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

縦偏極陽子陽子衝突におけるW生成のパリティを破るスピン非対称性の測定

Adare, A.*; 長谷川 勝一   ; 今井 憲一; 永宮 正治; 佐甲 博之   ; 佐藤 進  ; 谷田 聖   ; PHENIX Collaboration*; 他445名*

Adare, A.*; Hasegawa, Shoichi; Imai, Kenichi; Nagamiya, Shoji; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 445 of others*

We present midrapidity measurements from the PHENIX experiment of large parity-violating single-spin asymmetries of high transverse momentum electrons and positrons from decays, produced in longitudinally polarized collisions at center of mass energies of = 500 and 510 GeV. These asymmetries allow direct access to the antiquark polarized parton distribution functions due to the parity-violating nature of the -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, which exceeds previous PHENIX published results by a factor of more than 27. These high data probe the parton structure of the proton at mass scale and provide an important addition to our understanding of the antiquark parton helicity distribution functions at an intermediate Bjorken value of roughly .