Precision Measurement of the Neutron Spin Dependent Structure Functions

Technical Report · Sat Feb 01 04:00:00 EST 1997

DOI:https://doi.org/10.2172/1454175· OSTI ID:1454175

Kolomensky, Yury G. ^[1]

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1. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford Univ., CA (United States)

In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function $$g^{n}_{1}(x, Q^{2})$$ of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized ³He target. The high beam energy allowed us to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 ≤ $$x$$ ≤ 0.7 with an average $$Q^{2}$$ of 5 GeV$$^{2}$$. We report the integral of the spin dependent structure function in the measured range to be $$\int^{0.7}_{0.014}dx$$ $$g^{n}_{1}(x, 5$$ $$GeV^{2}) = -0.036 ± 0.0014(stat.) ± 0.005(syst.)$$. We observe relatively large values of $$g^{n}_{1}$$ at low $$x$$ that call into question the reliability of data extrapolation to $x → 0$. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. We perform a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure function $$g^{p}_{1}$$ and $$g^{n}_{1}$$ paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, we evolve the data to $$Q^{2} = 5 GeV^{2}$$, determine the first moments of the polarized structure functions of the proton and neutron, and find agreement with the Bjorken sum rule.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford Univ., CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1454175
• Report Number(s): SLAC-R--503
• Country of Publication: United States
• Language: English