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Title: Precise determination of the spin structure function g{sub 1} of the proton, deuteron, and neutron.

Abstract

Precise measurements of the spin structure functions of the proton g{sub 1}{sup p}x,Q{sup 2} and deuteron g{sub 1}{sup d}x,Q{sup 2} are presented over the kinematic range 0.0041 <= x <= 0.9 and 0.18 GeV{sup 2} <= Q{sup 2} <= 20 GeV{sup 2}. The data were collected at the HERMES experiment at DESY, in deep-inelastic scattering of 27.6 GeV longitudinally polarized positrons off longitudinally polarized hydrogen and deuterium gas targets internal to the HERA storage ring. The neutron spin structure function g{sub 1}{sup n} is extracted by combining proton and deuteron data. The integrals of g{sub 1}{sup p,d} at Q{sup 2} = 5 GeV{sup 2} are evaluated over the measured x range. Neglecting any possible contribution to the g{sub 1}{sup d} integral from the region x <= 0.021, a value of 0.330 {+-} 0.011(theo) {+-} 0.025(exp) {+-} 0.028(evol) is obtained for the flavor-singlet axial charge a{sub 0} in a leading-twist next-to-next-to-leading-order analysis.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE; FOR; National Science Foundation (NSF)
OSTI Identifier:
940204
Report Number(s):
ANL/PHY/JA-57155
Journal ID: ISSN 1550-7998; TRN: US0807047
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. D; Journal Volume: 75; Journal Issue: Jan. 1, 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
08 HYDROGEN; 43 PARTICLE ACCELERATORS; DEUTERIUM; DEUTERONS; HERA STORAGE RING; HYDROGEN; NEUTRONS; POSITRONS; PROTONS; SCATTERING; SPIN; STRUCTURE FUNCTIONS; TARGETS

Citation Formats

Airapetian, A., Akopov, N., Akopov, Z., Andrus, A., Aschenauer, E. C., El Alaoui, M. A., Jackson, H. E., Reimer, P. E., Sanjiev, I., The HERMES Collaboration, Physics, Univ. of Michigan, Yerevan Physics Inst., Univ. of Illinois, and DESY Lab.. Precise determination of the spin structure function g{sub 1} of the proton, deuteron, and neutron.. United States: N. p., 2007. Web. doi:10.1103/PhysRevD.75.012007.
Airapetian, A., Akopov, N., Akopov, Z., Andrus, A., Aschenauer, E. C., El Alaoui, M. A., Jackson, H. E., Reimer, P. E., Sanjiev, I., The HERMES Collaboration, Physics, Univ. of Michigan, Yerevan Physics Inst., Univ. of Illinois, & DESY Lab.. Precise determination of the spin structure function g{sub 1} of the proton, deuteron, and neutron.. United States. doi:10.1103/PhysRevD.75.012007.
Airapetian, A., Akopov, N., Akopov, Z., Andrus, A., Aschenauer, E. C., El Alaoui, M. A., Jackson, H. E., Reimer, P. E., Sanjiev, I., The HERMES Collaboration, Physics, Univ. of Michigan, Yerevan Physics Inst., Univ. of Illinois, and DESY Lab.. Mon . "Precise determination of the spin structure function g{sub 1} of the proton, deuteron, and neutron.". United States. doi:10.1103/PhysRevD.75.012007.
@article{osti_940204,
title = {Precise determination of the spin structure function g{sub 1} of the proton, deuteron, and neutron.},
author = {Airapetian, A. and Akopov, N. and Akopov, Z. and Andrus, A. and Aschenauer, E. C. and El Alaoui, M. A. and Jackson, H. E. and Reimer, P. E. and Sanjiev, I. and The HERMES Collaboration and Physics and Univ. of Michigan and Yerevan Physics Inst. and Univ. of Illinois and DESY Lab.},
abstractNote = {Precise measurements of the spin structure functions of the proton g{sub 1}{sup p}x,Q{sup 2} and deuteron g{sub 1}{sup d}x,Q{sup 2} are presented over the kinematic range 0.0041 <= x <= 0.9 and 0.18 GeV{sup 2} <= Q{sup 2} <= 20 GeV{sup 2}. The data were collected at the HERMES experiment at DESY, in deep-inelastic scattering of 27.6 GeV longitudinally polarized positrons off longitudinally polarized hydrogen and deuterium gas targets internal to the HERA storage ring. The neutron spin structure function g{sub 1}{sup n} is extracted by combining proton and deuteron data. The integrals of g{sub 1}{sup p,d} at Q{sup 2} = 5 GeV{sup 2} are evaluated over the measured x range. Neglecting any possible contribution to the g{sub 1}{sup d} integral from the region x <= 0.021, a value of 0.330 {+-} 0.011(theo) {+-} 0.025(exp) {+-} 0.028(evol) is obtained for the flavor-singlet axial charge a{sub 0} in a leading-twist next-to-next-to-leading-order analysis.},
doi = {10.1103/PhysRevD.75.012007},
journal = {Phys. Rev. D},
number = Jan. 1, 2007,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Precise measurements of the spin structure functions of the proton g{sub 1}{sup p}(x,Q{sup 2}) and deuteron g{sub 1}{sup d}(x,Q{sup 2}) are presented over the kinematic range 0.0041{<=}x{<=}0.9 and 0.18 GeV{sup 2}{<=}Q{sup 2}{<=}20 GeV{sup 2}. The data were collected at the HERMES experiment at DESY, in deep-inelastic scattering of 27.6 GeV longitudinally polarized positrons off longitudinally polarized hydrogen and deuterium gas targets internal to the HERA storage ring. The neutron spin structure function g{sub 1}{sup n} is extracted by combining proton and deuteron data. The integrals of g{sub 1}{sup p,d} at Q{sup 2}=5 GeV{sup 2} are evaluated over the measured xmore » range. Neglecting any possible contribution to the g{sub 1}{sup d} integral from the region x{<=}0.021, a value of 0.330{+-}0.011(theo){+-}0.025(exp){+-}0.028(evol) is obtained for the flavor-singlet axial charge a{sub 0} in a leading-twist next-to-next-to-leading-order analysis.« less
  • The measurements of the spin-dependent structure function {ital g}{sub 1} of the proton and, briefly, of the deuteron in polarized deep inelastic scattering are presented. Implications for our understanding of the internal spin structure of the nucleon are discussed. Data are in disagreement with the Ellis-Jaffe sum rule at a two standard deviation level. The Bjorken sum rule is confirmed to within 10{percent} of its theoretical value (one standard deviation level). {copyright} {ital 1995 American Institute of Physics.}
  • 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 nuclear effects in the spin-dependent structure functions {ital g}{sup {ital D}}{sub 1} and {ital b}{sup {ital D}}{sub 2} are calculated in the relativistic approach based on the Bethe-Salpeter equation with a realistic meson-exchange potential. The results of calculations are compared with the non-relativistic calculations. The problem of extraction of the neutron spin structure function, {ital g}{sup {ital n}}{sub 1}, from the deuteron data is discussed.
  • We report on a precision measurement of the neutron spin structure function g{sup n}{sub 1} using deep inelastic scattering of polarized electrons by polarized {sup 3}He . For the kinematic range 0.014{lt}x{lt}0.7 and 1{lt}Q{sup 2}{lt}17(GeV /c){sup 2} , we obtain {integral}{sub 0.014}{sup 0.7}g{sup n}{sub 1}(x)dx={minus}0.036{plus_minus}0.004(stat){plus_minus}0.005(syst) at an average Q{sup 2}=5(GeV/c){sup 2}. We find relatively large negative values for g{sup n}{sub 1} at low x . The results call into question the usual Regge theory method for extrapolating to x=0 to find the full neutron integral {integral}{sub 0}{sup 1}g{sup n}{sub 1}(x)dx, needed for testing the quark-parton model and QCD sum rules.more » {copyright} {ital 1997} {ital The American Physical Society}« less