Precision measurement of the neutron spin asymmetries and spin-dependent structure functions in the valence quark region
We report on measurements of the neutron spin asymmetries A 1,2n and polarized structure functions g 1,2n at three kinematics in the deep inelastic region, with x=0.33, 0.47, and 0.60 and Q2=2.1, 3.5, and 4.8 (GeV/c) 2, respectively. These measurements were performed using a 5.7 GeV longitudinally polarized electron beam and a polarized 3He target. The results for A1n and g1n at x=0.33 are consistent with previous world data and, at the two higher-x points, have improved the precision of the world data by about an order of magnitude. The new A1n data show a zero crossing around x=0.47 and the value at x=0.60 is significantly positive. These results agree with a next-to-leading-order QCD analysis of previous world data. The trend of data at high x agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (PQCD) assuming hadron helicity conservation. Results for A2n and g2n have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment d 2n was evaluated and the new result has improved the precision of this quantity by about a factor of 2. When combined with the world proton data, polarized quark distribution functions were extracted from the new g1n/F1n values based on the quark-parton model. While results for Δu/u agree well with predictions from various models, results for Δd/d disagree with the leading-order PQCD prediction when hadron helicity conservation is imposed.
Zheng, X; Aniol, K; Armstrong, DS; Averett, TD; Bertozzi, W; Binet, S; Burtin, E; Busato, E; Butuceanu, C; Calarco, J; Camsonne, A; Cates, GD; Chai, Z; Chen, JP; Choi, S; Chudakov, E; Cusanno, F; De Leo, R; Deur, A; Dieterich, S; Dutta, D; Finn, JM; Frullani, S; Gao, H; Gao, J; Garibaldi, F; Gilad, S; Gilman, R; Gomez, J; Hansen, JO; Higinbotham, DW; Hinton, W; Horn, T; De Jager, CW; Jiang, X; Kaufman, L; Kelly, J; Korsch, W; Kramer, K; LeRose, J; Lhuillier, D; Liyanage, N; Margaziotis, DJ; Marie, F; Markowitz, P; McCormick, K; Meziani, ZE; Michaels, R; Moffit, B; Nanda, S; Neyret, D; Phillips, SK; Powell, A; Pussieux, T; Reitz, B; Roche, J; Roché, R; Roedelbronn, M; Ron, G; Rvachev, M; Saha, A; Savvinov, N; Singh, J; Širca, S; Slifer, K; Solvignon, P; Souder, P; Steiner, DJ; Strauch, S; Sulkosky, V; Tobias, A; Urciuoli, G; Vacheret, A; Wojtsekhowski, B; Xiang, H; Xiao, Y; Xiong, F; Zhang, B; Zhu, L; Zhu, X; Zołnierczuk, PA
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