Proton distribution radii of $^{12-19}$C illuminate features of neutron   halos
  Proton radii of $^{12-19}$C densities derived from first accurate charge changing cross section measurements at 900$A$ MeV with a carbon target are reported. A thick neutron surface evolves from $\sim$ 0.5 fm in $^{15}$C to $\sim$ 1 fm in $^{19}$C. The halo radius in $^{19}$C is found to be 6.4$\pm$0.7 fm as large as $^{11}$Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce well the radii. 
R. Kanungo, W. Horiuchi, G. Hagen, G. R. Jansen, P. Navratil, F.   Ameil, J. Atkinson, Y. Ayyad, D. Cortina-Gil, I. Dillmann...
nucl-ex nucl-th