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Title: Proton Spin Structure in the Resonance Region

Abstract

We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV<W<1.910 GeV) at an average four momentum transfer of Q{sup 2}=1.3 GeV{sup 2}. Using the Jefferson Lab polarized electron beam, a spectrometer, and a polarized solid target, we measured the asymmetries A{sub parallel} and A{sub perpendicular} to high precision, and extracted the asymmetries A{sub 1} and A{sub 2}, and the spin structure functions g{sub 1} and g{sub 2}. We found a notably nonzero A{sub perpendicular}, significant contributions from higher-twist effects, and only weak support for polarized quark-hadron duality.

Authors:
 [1];  [2]; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1]; more »;  [3] « less
  1. University of Virginia, Charlottesville, Virginia 22903 (United States)
  2. (United States)
  3. Yerevan Physics Institute, Yerevan (Armenia) (and others)
Publication Date:
OSTI Identifier:
20951184
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 13; Other Information: DOI: 10.1103/PhysRevLett.98.132003; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; CEBAF ACCELERATOR; ELECTRON BEAMS; FOUR MOMENTUM TRANSFER; GEV RANGE 01-10; POLARIZED BEAMS; PROTONS; QUARK-HADRON INTERACTIONS; RESONANCE; SPIN; STRUCTURE FUNCTIONS

Citation Formats

Wesselmann, F. R., Norfolk State University, Norfolk, Virginia 23504, Slifer, K., Tajima, S., Crabb, D., Day, D., Frlez, E., Lindgren, R., McKee, P., McNulty, D., Norum, B., Pocanic, D., Prok, Y., Rondon, O. A., Sawatzky, B., Smith, C., Wang, K., Zeier, M., Zhu, H., Aghalaryan, A., and Asaturyan, R. Proton Spin Structure in the Resonance Region. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.132003.
Wesselmann, F. R., Norfolk State University, Norfolk, Virginia 23504, Slifer, K., Tajima, S., Crabb, D., Day, D., Frlez, E., Lindgren, R., McKee, P., McNulty, D., Norum, B., Pocanic, D., Prok, Y., Rondon, O. A., Sawatzky, B., Smith, C., Wang, K., Zeier, M., Zhu, H., Aghalaryan, A., & Asaturyan, R. Proton Spin Structure in the Resonance Region. United States. doi:10.1103/PHYSREVLETT.98.132003.
Wesselmann, F. R., Norfolk State University, Norfolk, Virginia 23504, Slifer, K., Tajima, S., Crabb, D., Day, D., Frlez, E., Lindgren, R., McKee, P., McNulty, D., Norum, B., Pocanic, D., Prok, Y., Rondon, O. A., Sawatzky, B., Smith, C., Wang, K., Zeier, M., Zhu, H., Aghalaryan, A., and Asaturyan, R. Fri . "Proton Spin Structure in the Resonance Region". United States. doi:10.1103/PHYSREVLETT.98.132003.
@article{osti_20951184,
title = {Proton Spin Structure in the Resonance Region},
author = {Wesselmann, F. R. and Norfolk State University, Norfolk, Virginia 23504 and Slifer, K. and Tajima, S. and Crabb, D. and Day, D. and Frlez, E. and Lindgren, R. and McKee, P. and McNulty, D. and Norum, B. and Pocanic, D. and Prok, Y. and Rondon, O. A. and Sawatzky, B. and Smith, C. and Wang, K. and Zeier, M. and Zhu, H. and Aghalaryan, A. and Asaturyan, R.},
abstractNote = {We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV<W<1.910 GeV) at an average four momentum transfer of Q{sup 2}=1.3 GeV{sup 2}. Using the Jefferson Lab polarized electron beam, a spectrometer, and a polarized solid target, we measured the asymmetries A{sub parallel} and A{sub perpendicular} to high precision, and extracted the asymmetries A{sub 1} and A{sub 2}, and the spin structure functions g{sub 1} and g{sub 2}. We found a notably nonzero A{sub perpendicular}, significant contributions from higher-twist effects, and only weak support for polarized quark-hadron duality.},
doi = {10.1103/PHYSREVLETT.98.132003},
journal = {Physical Review Letters},
number = 13,
volume = 98,
place = {United States},
year = {Fri Mar 30 00:00:00 EDT 2007},
month = {Fri Mar 30 00:00:00 EDT 2007}
}
  • We have measured the proton and deuteron spin structure functions g{sup p}{sub 1} and g{sup d}{sub 1} in the region of the nucleon resonances for W{sup 2}{lt}5 GeV{sup 2} and Q{sup 2}{approx_equal}0.5 and Q{sup 2}{approx_equal}1.2 GeV{sup 2} by inelastically scattering 9.7 GeV polarized electrons off polarized {sup 15}NH{sub 3} and {sup 15}ND{sub 3} targets. We observe significant structure in g{sup p}{sub 1} in the resonance region. We have used the present results, together with the deep-inelastic data at higher W{sup 2}, to extract {Gamma}(Q{sup 2}){equivalent_to}0=g{sub 1}(x,Q{sup 2})dx. This is the first information on the low-Q{sup 2} evolution of {Gamma} towardmore » the Gerasimov-Drell-Hearn limit at Q{sup 2}=0. {copyright} {ital 1997} {ital The American Physical Society}« less
  • The RSS collaboration has measured the spin structure functions g{sub 1} and g{sub 2} of the proton at Jefferson Lab using the lab's polarized electron beam, the Hall C HMS spectrometer and the UVa polarized solid target. The asymmetries A{sub parallel} and A{sub perp} were measured at the elastic peak and in the region of the nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum transfer of Q{sup 2} = 1.3 GeV{sup 2}. The extracted spin structure functions and their kinematic dependence make a significant contribution in the study of higher-twist effects and polarized dualitymore » tests.« less
  • We measured the inclusive electron-proton cross section in the nucleon resonance region (W<2.5 GeV) at momentum transfers Q2 below 4.5 (GeV/c)2 with the CLAS detector. The large acceptance of CLAS allowed the measurement of the cross section in a large, contiguous two-dimensional range of Q2 and x, making it possible to perform an integration of the data at fixed Q2 over the significant x interval. >From these data we extracted the structure function F2 and, by including other world data, we studied the Q2 evolution of its moments, Mn(Q2), in order to estimate higher twist contributions. The small statistical andmore » systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and will require significant improvements in theoretical predictions if a meaningful comparison with these new experimental results is to be made.« less
  • In this paper, we investigate the effects of the quantity {sigma}{sub {ital TS}} on the spin structure functions of nucleons in the resonance region. The Schwinger sum rule for the spin structure function {ital g}{sub 2}({ital x},{ital Q}{sup 2}) at the real photon limit is derived for the nucleon treated as a composite system, and it provides a crucial constraint on the longitudinal transition operator which has not been treated consistently in the literature. The longitudinal amplitude {ital S}{sub 1/2} is evaluated in the quark model with the transition operator that generates the Schwinger sum rule. The numerical results ofmore » the quantity {sigma}{sub {ital TS}} are presented for both spin structure functions {ital g}{sub 1}({ital x},{ital Q}{sup 2}) and {ital g}{sub 2}({ital x},{ital Q}{sup 2}) in the resonance region. Our results show that this quantity plays an important role in the low {ital Q}{sup 2} region, which can be tested in future experiments at CEBAF. {copyright} {ital 1996 The American Physical Society.}« less