Precision Determination of the Neutron Spin Structure Function g1n

TL;DR

This paper presents a precise measurement of the neutron spin structure function g1n using polarized deep inelastic scattering, revealing significant negative values at low x and challenging existing extrapolation methods for the full integral.

Contribution

It provides the first high-precision data on g1n over a broad kinematic range, questioning the validity of traditional Regge theory extrapolations.

Findings

g1n is significantly negative at low x

The measured integral is -0.036 with uncertainties

Results challenge standard extrapolation methods for full neutron integral

Abstract

We report on a precision measurement of the neutron spin structure function $g^n_1$ using deep inelastic scattering of polarized electrons by polarized ^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2, we obtain $\int^{0.7}_{0.014} g^n_1(x)dx = -0.036 \pm 0.004 (stat) \pm 0.005 (syst)$ at an average $Q^2=5 (GeV/c)^2$. We find relatively large negative values for $g^n_1$ at low $x$. The results call into question the usual Regge theory method for extrapolating to x=0 to find the full neutron integral $\int^1_0 g^n_1(x)dx$, needed for testing quark-parton model and QCD sum rules.