Spin Structure Function Measurements from E143 at SLAC
Recent high statistics measurements of the nucleon spin structure functions by the E143 Collaboration are presented. The structure functions g{sub 1}{sup n} and g{sub 1}{sup d} have been measured over the range 0.029 < x < 0.8 and 1.3 < Q{sup 2} < 10 (GeV/c){sup 2} using deep inelastic scattering of polarized electrons from polarized ammonia and deuterated ammonia targets. Evaluation of the integral {Gamma}{sub 1}{sup p} = {integral}{sub 0}{sup 1} g{sub 1}{sup p}(x, Q{sup 2})dx at fixed Q{sup 2} = 3 (GeV/c){sup 2} yields 0.127 {+-} 0.004 {+-} 0.010, in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160 {+-} 0.006. The integral {Gamma}{sub 1}{sup d} = {integral}{sub 0}{sup 1} g{sub 1}{sup d}(x,Q{sup 2})dx also evaluated at fixed Q{sup 2} = 3 (GeV/c){sup 2} gives 0.041 {+-} 0.004 {+-} 0.004, again below the Ellis-Jaffe sum rule prediction of 0.068 {+-} 0.005. From g{sub 1}{sup p} and g{sub 1}{sup d}, the neutron structure function g{sub 1}{sup n} can be computed with {Gamma}{sub 1}{sup n} measured as -0.037 {+-} 0.008 {+-} 0.010. Combined with the measurement of g{sub 1}{sup p}, they find {Gamma}{sub 1}{sup p} - {Gamma}{sub 1}{sup n} = 0.163 {+-} 0.010 {+-} 0.016 which agrees with the prediction of the Bjorken sum rule with {Omicron}({alpha}{sub s}{sup 3}) corrections, {Gamma}{sub 1}{sup p}-{gamma}{sub 1}{sup n} = 0.171 {+-} 0.008. In the quark-parton model, this implies that the net helicity carried by the quarks is {Delta}q = 0.34 {+-} 0.04.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 813299
- Report Number(s):
- SLAC-PUB-10046; TRN: US0303840
- Resource Relation:
- Other Information: Paper presented at the 22nd Annual SLAC Summer Institute on Particle Physics: Particle Physics, Astrophysics and Cosmology, Stanford, CA (US), 08/08/1994--08/19/1994; PBD: 16 Jul 2003
- Country of Publication:
- United States
- Language:
- English
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