We report on a precision measurement of the neutron spin structure function gn1 using deep inelastic scattering of polarized electrons by polarized 3He. For the kinematic range 0.014 < x < 0.7 and 1 < Q2 < 17(GeV/c)2, we obtain ∫0.0140.7 gn1(x)dx = −0.036 ± 0.004(stat) ± 0.005(syst) at an average Q2 = 5(GeV/c)2. We find relatively large negative values for gn1 at low x. The results call into question the usual Regge theory method for extrapolating to x = 0 to find the full neutron integral ∫ 1gn1(x) dx, needed for testing the quark-parton model and QCD sum rules.
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