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Measurements of double-helicity asymmetries in inclusive $$J/psi$$ production in longitudinally polarized $$p+p$$ collisions at $$sqrt{s}=510$$ GeV

$$sqrt{s}=510$$GeVでの縦偏極陽子衝突におけるインクルーシブ$$J/psi$$生成の二重スピン非対称性の測定

Adare, A.*; 今井 憲一; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他328名*

Adare, A.*; Imai, Kenichi; Hasegawa, Shoichi; Nagamiya, Shoji; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 328 of others*

We report the double-helicity asymmetry, $$A_{LL}^{J/psi}$$, in inclusive $$J/psi$$ production at forward rapidity as a function of transverse momentum $$p_T$$ and rapidity $$|y|$$. The data analyzed were taken during $$sqrt{s}=510$$ GeV longitudinally polarized $$p+p$$ collisions at the Relativistic Heavy Ion Collider in the 2013 run using the PHENIX detector. At this collision energy, $$J/psi$$ particles are predominantly produced through gluon-gluon scatterings, thus $$A_{LL}^{J/psi}$$ is sensitive to the gluon polarization inside the proton. We measured $$A_{LL}^{J/psi}$$ by detecting the decay daughter muon pairs $$mu^+mu^-$$ within the PHENIX muon spectrometers in the rapidity range $$1.2<|y|<2.2$$. In this kinematic range, we measured the $$A_{LL}^{J/psi}$$ to be $$0.012 pm 0.010 ({rm stat}) pm 0.003 ({rm syst})$$. The $$A_{LL}^{J/psi}$$ can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken $$x$$: one at moderate range $$x cong 5 times 10^{-2}$$ where recent data of jet and $$pi^0$$ double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-x region $$x cong 2 times 10^{-3}$$ Thus our new results could be used to further constrain the gluon polarization for $$x < 5 times 10^{-2}$$.

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パーセンタイル:59.4

分野:Astronomy & Astrophysics

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