[Gdh_lowq2] Abstract for PANIC 2011

[Sarah Phillips]

Dear EG4 collaborators,

      I would like to submit the following abstract for PANIC 2011 (see 
http://web.mit.edu/panic11/index.html).  Please let me know if you have 
comments.  The abstract deadline is tomorrow, so please do not delay in 
sending your comments!  I apologize for the last-minute nature of this 
request, and thank you for your time.

With Regards,

Sarah



Nucleon Spin Structure and the JLab CLAS EG4 Experiment


Our picture of the nucleon is not complete without a thorough 
understanding of the spin structure of the nucleon.  One way to access 
spin information is by measuring the spin structure functions g1 and g2, 
which are fundamental spin observables which characterize the deviation of 
the nucleon's spin-dependent properties from point-like behavior. 
Knowledge of g1 at low Q^2 would provide tests of chiral perturbation 
theory predictions in the resonance region.  However, data on g1 for the 
proton at very low Q^2 are lacking.  The CLAS EG4 experiment was performed 
at Jefferson Lab to determine the generalized GDH sum for the proton and 
the neutron at very low Q^2 from 0.015 to 0.5 (GeV/c)^2.   The experiment 
used Hall B's CLAS (CEBAF Large Acceptance Spectrometer) to perform a 
measurement of the helicity-dependent inclusive cross section differences 
for the scattering of polarized electrons from polarized protons and 
deuterons in solid polarized NH3 and ND3 targets.  From this absolute 
polarized cross section measurement, we will be able to extract the 
inclusive spin structure function g1 for the proton and the deuteron.  In 
addition to the spin structure functions that can be obtained from the 
inclusive measurement, the same data can be used to extract pion 
electroproduction asymmetries in the resonance region through the analysis 
of exclusive channels.  Upon completion of the analysis, the inclusive 
results will give a good test of chiral perturbation theory predictions. 
An overview of the EG4 experiment will be given, as well as preliminary 
results for the inclusive and exclusive analyses.