Incident-energy dependence of the fragmentation mechanism reflecting the cluster structure of the ¹⁹B nucleus

We investigate the fragmentation mechanism reflecting the cluster structure of the ¹⁹B nucleus. We perform antisymmetrized molecular dynamics (AMD) calculations of ¹⁹B+¹⁴N and ¹³B+¹⁴N reactions, and compare ¹⁹B fragmentation with ¹³B fragmentation. The neutron drip-line nucleus ¹⁹B has been predicted to have a well-developed cluster structure in its ground state while the neutron closed-shell nucleus ¹³B has no clustering features in its structure. The clustering structure of ¹⁹B is reflected in its fragmentation as the dynamical cluster breakup into He and Li isotopes, depending on the incident energy. In the low-incident-energy region around 30 MeV/nucleon, dynamical cluster breakup of ¹⁹B occurs and brings about an abundance of He and Li isotopes in ¹⁹B fragmentation compared with those in ¹³B fragmentation. In the high-incident-energy region above 50 MeV/nucleon, dynamical cluster breakup of ¹⁹B hardly occurs and the cluster structure of the ¹⁹B nucleus is not reflected in its fragmentation. We suggest here the coincident experiment between He and Li isotopes as an experimental way to confirm whether the ¹⁹B nucleus has a cluster structure in its ground state or not.