Low Q^2 measurements of the proton form factor ratio $mu_p G_E / G_M$
  We present an updated extraction of the proton electromagnetic form factor ratio, mu_p G_E/G_M, at low Q^2. The form factors are sensitive to the spatial distribution of the proton, and precise measurements can be used to constrain models of the proton. An improved selection of the elastic events and reduced background contributions yielded a small systematic reduction in the ratio mu_p G_E/G_M compared to the original analysis. 
G. Ron, X. Zhan, J. Glister, B. Lee, K. Allada, W. Armstrong, J.   Arrington, A. Beck, F. Benmokhtar, B.L. Berman, W. Boegli...
nucl-ex nucl-th