# Moments of the Spin Structure Functions $g_1^p$ and $g_1^d$ for 0.05 $< Q^2 < 3.0 GeV^2$

Abstract : The spin structure functions $g_1$ for the proton and the deuteron have been measured over a wide kinematic range in x and $Q^2$ using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized $NH_3$ and $ND_3$ targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05 $< Q^2 < 5 GeV^2$ and W < 3 GeV. The first moments of $g_1$ for the proton and deuteron are presented -- both have a negative slope at low $Q^2$, as predicted by the extended Gerasimov-Drell-Hearn sum rule. The first result for the generalized forward spin polarizability of the proton $\gamma_0^p$ is also reported, and shows evidence of scaling above $Q^2 = 1.5 GeV^2$. Although the first moments of $g_1$ are consistent with Chiral Perturbation Theory (ChPT) calculations up to approximately $Q^2 = 0.06 GeV^2$, a significant discrepancy is observed between the $\gamma_0^p$ data and ChPT for$\ gamma_0^p$, even at the lowest $Q^2$.
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Submitted on : Tuesday, February 19, 2008 - 4:44:02 PM
Last modification on : Wednesday, September 16, 2020 - 4:07:55 PM

### Citation

Y. Prok, P. Bosted, V. D. Burkert, A. Deur, K. V. Dharmawardane, et al.. Moments of the Spin Structure Functions $g_1^p$ and $g_1^d$ for 0.05 $< Q^2 < 3.0 GeV^2$. Physics Letters B, Elsevier, 2009, 672, pp.12-16. ⟨10.1016/j.physletb.2008.12.063⟩. ⟨in2p3-00257582⟩

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