Phys. Rev. Lett.
92,
012004
(2004)
[5 pages]
Precision Measurement of the Neutron Spin AsymmetryA1n and Spin-Flavor Decomposition in the Valence Quark Region
X. Zheng et al. Jefferson Lab Hall A Collaboration
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X. Zheng13, K. Aniol2, D. S. Armstrong22, T. D. Averett8,22, W. Bertozzi13, S. Binet21, E. Burtin17, E. Busato16, C. Butuceanu22, J. Calarco14, A. Camsonne3, G. D. Cates21, Z. Chai13, J.-P. Chen8, Seonho Choi20, E. Chudakov8, F. Cusanno7, R. De Leo7, A. Deur21, S. Dieterich16, D. Dutta13, J. M. Finn22, S. Frullani7, H. Gao13, J. Gao1, F. Garibaldi7, S. Gilad13, R. Gilman8,16, J. Gomez8, J.-O. Hansen8, D. W. Higinbotham13, W. Hinton15, T. Horn11, C. W. de Jager8, X. Jiang16, L. Kaufman12, J. Kelly11, W. Korsch10, K. Kramer22, J. LeRose8, D. Lhuillier17, N. Liyanage8, D. J. Margaziotis2, F. Marie17, P. Markowitz4, K. McCormick9, Z.-E. Meziani20, R. Michaels8, B. Moffit22, S. Nanda8, D. Neyret17, S. K. Phillips22, A. Powell22, T. Pussieux17, B. Reitz8, J. Roche22, R. Roche5, M. Roedelbronn6, G. Ron19, M. Rvachev13, A. Saha8, N. Savvinov11, J. Singh21, S. Širca13, K. Slifer20, P. Solvignon20, P. Souder18, D. J. Steiner22, S. Strauch16, V. Sulkosky22, A. Tobias21, G. Urciuoli7, A. Vacheret12, B. Wojtsekhowski8, H. Xiang13, Y. Xiao13, F. Xiong13, B. Zhang13, L. Zhu13, X. Zhu22, and P. A. Żołnierczuk10 (Jefferson Lab Hall A Collaboration)
1California Institute of Technology, Pasadena, California 91125, USA
2California State University, Los Angeles, Los Angeles, California 90032, USA
3Université Blaise Pascal Clermont-Ferrand et CNRS/IN2P3 LPC 63, 177 Aubière Cedex, France
4Florida International University, Miami, Florida 33199, USA
5Florida State University, Tallahassee, Florida 32306, USA
6University of Illinois, Urbana, Illinois 61801, USA
7Istituto Nazionale di Fisica Nucleare, Sezione Sanità, 00161 Roma, Italy
8Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
9Kent State University, Kent, Ohio 44242, USA
10University of Kentucky, Lexington, Kentucky 40506, USA
11University of Maryland, College Park, Maryland 20742, USA
12University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
13Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
14University of New Hampshire, Durham, New Hampshire 03824, USA
15Old Dominion University, Norfolk, Virginia 23529, USA
16Rutgers, The State University of New Jersey, Piscataway, New Jersey 08855, USA
17CEA Saclay, DAPNIA/SPhN, F-91191 Gif sur Yvette, France
18Syracuse University, Syracuse, New York 13244, USA
19University of Tel Aviv, Tel Aviv 69978, Israel
20Temple University, Philadelphia, Pennsylvania 19122, USA
21University of Virginia, Charlottesville, Virginia 22904, USA
22College of William and Mary, Williamsburg, Virginia 23187, USA
Received 23 April 2003; published 7 January 2004
We have measured the neutron spin asymmetry A1n with high precision at three kinematics in the deep inelastic region at x=0.33, 0.47, and 0.60, and Q2=2.7, 3.5, and 4.8 (GeV/c)2, respectively. Our results unambiguously show, for the first time, that A1n crosses zero around x=0.47 and becomes significantly positive at x=0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (PQCD) analyses based on the earlier data. However they deviate from PQCD predictions based on hadron helicity conservation.
© 2004 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.92.012004
DOI:
10.1103/PhysRevLett.92.012004
PACS:
13.60.Hb, 24.85.+p, 25.30.–c
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