Precision measurement of the neutron spin asymmetries and spin-dependent structure functions in the valence quark region

X. Zheng*, K. Aniol, D. S. Armstrong, T. D. Averett, W. Bertozzi, S. Binet, E. Burtin, E. Busato, C. Butuceanu, J. Calarco, A. Camsonne, G. D. Cates, Z. Chai, J. P. Chen, Seonho Choi, E. Chudakov, F. Cusanno, R. De Leo, A. Deur, S. DieterichD. Dutta, J. M. Finn, S. Frullani, H. Gao, J. Gao, F. Garibaldi, S. Gilad, R. Gilman, J. Gomez, J. O. Hansen, D. W. Higinbotham, W. Hinton, T. Horn, C. W. De Jager, X. Jiang, L. Kaufman, J. Kelly, W. Korsch, K. Kramer, J. LeRose, D. Lhuillier, N. Liyanage, D. J. Margaziotis, F. Marie, P. Markowitz, K. McCormick, Z. E. Meziani, R. Michaels, B. Moffit, S. Nanda, D. Neyret, S. K. Phillips, A. Powell, T. Pussieux, B. Reitz, J. Roche, R. Roché, M. Roedelbronn, G. Ron, M. Rvachev, A. Saha, N. Savvinov, J. Singh, S. Širca, K. Slifer, P. Solvignon, P. Souder, D. J. Steiner, S. Strauch, V. Sulkosky, A. Tobias, G. Urciuoli, A. Vacheret, B. Wojtsekhowski, H. Xiang, Y. Xiao, F. Xiong, B. Zhang, L. Zhu, X. Zhu, P. A. Zołnierczuk

*Corresponding author for this work

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Abstract

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 g2 n 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.

Original languageAmerican English
Article number065207
Pages (from-to)065207-1-065207-25
JournalPhysical Review C - Nuclear Physics
Volume70
Issue number6
DOIs
StatePublished - Dec 2004
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank the personnel of Jefferson Lab for their efforts which resulted in the successful completion of the experiment. We thank S. J. Brodsky, L. Gamberg, N. Isgur, X. Ji, E. Leader, W. Melnitchouk, D. Stamenov, J. Soffer, M. Strikman, A. Thomas, M. Wakamatsu, H. Weigel, and their collaborators for theoretical support and helpful discussions. This work was supported by the Department of Energy (DOE), the National Science Foundation, the Italian Istituto Nazionale di Fisica Nucleare, the French Institut National de Physique Nucléaire et de Physique des Particules, the French Commissariat à l’Énergie Atomique, and the Jeffress Memorial Trust. The Southeastern Universities Research Association operates the Thomas Jefferson National Accelerator Facility for the DOE under contract DE-AC05-84ER40150.

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