A new approach for deducing rms proton radii from charge-changing reactions of neutron-rich nuclei and the reaction-target dependence.

We report the charge-changing cross sections (σ _cc ) of 24 p-shell nuclides on both hydrogen and carbon at about 900A MeV, of which ^8,9 Li, ^10-12 Be, ^10,14,15 B, ^14,15,17-22 N and ¹⁶ O on hydrogen and ^8,9 Li on carbon are for the first time. Benefiting from the data set, we found a new and robust relationship between the scaling factor of the Glauber model calculations and the separation energies of the nuclei of interest on both targets. This allows us to deduce proton radii (R _p ) for the first time from the cross sections on hydrogen. Nearly identical R _p values are deduced from both target data for the neutron-rich carbon isotopes; however, the R _p from the hydrogen target is systematically smaller in the neutron-rich nitrogen isotopes. This calls for further experimental and theoretical investigations.
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