Moments of the spin structure functions g1p and g1d for 0.05<Q<3.0 GeV
Abstract
The spin structure functions g for the proton and the deuteron have been measured over a wide kinematic range in x and Q using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH3 and ND3 targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05<Q<5 GeV and W<3 GeV. The first moments of g for the proton and deuteron are presented - both have a negative slope at low Q, as predicted by the extended Gerasimov-Drell-Hearn sum rule. The first extraction of the generalized forward spin polarizability of the proton γ0p is also reported. This quantity shows strong Q dependence at low Q. Our analysis of the Q evolution of the first moment of g shows agreement in leading order with Heavy Baryon Chiral Perturbation Theory. However, a significant discrepancy is observed between the γ0p data and Chiral Perturbation calculations for γ0p, even at the lowest Q.
- Publication:
-
Physics Letters B
- Pub Date:
- February 2009
- DOI:
- 10.1016/j.physletb.2008.12.063
- arXiv:
- arXiv:0802.2232
- Bibcode:
- 2009PhLB..672...12C
- Keywords:
-
- 13.60.Hb;
- 13.88.+e;
- 14.20.Dh;
- Total and inclusive cross sections;
- Polarization in interactions and scattering;
- Protons and neutrons;
- Nuclear Experiment
- E-Print:
- Final version as published in PLB. Added a parametrization of world data at high Q^2 to Fig. 3