Extracting the electric dipole breakup cross section of one-neutron halo nuclei from inclusive breakup observables

We discuss how to extract an electric dipole (E1) breakup cross section σ(E1) from one-neutron removal cross sections measured at 250 MeV/nucleon by using ¹²C and ²⁰⁸Pb targets, σ^C _-1n and σ^Pb_-1n, respectively. It is shown that, within about 5% error, σ(E1) can be obtained by subtracting Γσ^C_-1n from σ^Pb _-1n, as assumed in preceding studies. However, for the reaction of weakly bound projectiles, the scaling factor Γ is found to be about twice as large as that usually adopted. As a result, we obtain a 13-20% smaller σ(E1) of ³¹Ne at 250 MeV/nucleon than extracted in a previous analysis of experimental data. By compiling the values of Γ obtained for several projectiles, Γ = (2.30 ± 0.41) exp(-S_n) + (2.43 ± 0.21) is obtained, where S_n is the neutron separation energy. The target mass-number dependence of the nuclear parts of the one-neutron removal cross section and the elastic breakup cross section is also investigated.