Moments of the Spin Structure Functions g1p and g1d for 0.05 < Q2 < 3.0 GeV2
The spin structure functions $$g_1$$ for the proton and the deuteron have been measured over a wide kinematic range in $$x$$ and \Q2 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$$ for the proton and deuteron are presented -- both have a negative slope at low \Q2, as predicted by the extended Gerasimov-Drell-Hearn sum rule. The first result for the generalized forward spin polarizability of the proton $$\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 \Q2.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-060R23177
- OSTI ID:
- 956181
- Report Number(s):
- JLAB-PHY-08-778; arXiv:0802.2232; DOE/OR/23177-0301; PYLBAJ; TRN: US1004914
- Journal Information:
- Physics Letters B, Vol. 672; ISSN 0370-2693
- Country of Publication:
- United States
- Language:
- English
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