Identification for Ground-state ⁸Be in ¹²C+²⁰⁹Bi Reaction Based on Kinematic Reconstruction

For heavy-ion nuclear reactions induced by the weakly-bound ^6,7Li and tightly-bound ¹²C at near Coulomb-barrier energy region, plenty of α products have been detected experimentally in the early studies. However, the reaction mechanisms of heavy-ions in the near Coulomb-barrier energy region are complex. The origins of α particles still remain unsolved. For lighter projectiles such as ^6,7Li, and ⁹Be, α particles may originate from inelastic excitation followed by breakup process, or resonant states of projectile-like nuclei like ⁸Be populated by nucleon transfer. The subsequent breakup of ⁸Be poses a significant challenge for the experimental identification for ⁸Be. For tightly-bound nuclei like ¹²C, the situation is equally complex. Disentangling the sources of α particles and identifying the reaction mechanisms are essential for developing the low-energy heavy-ion reaction theory. However, due to the limitations of previous silicon detector technology, the kinematic coincidence measurements for the two breakup products were scare, particularly in the direct determination of the reaction channel (¹²C, ⁸Be→2α). For identifying the ground state ⁸Be, the experiment using kinematic reconstruction method was carried out at the R60º nuclear reaction terminal of the Beijing HI-13 Tandem Accelerator at the China Institute of Atomic Energy. Two ∆E-E silicon-strip detector telescopes were used for a kinematic coincidence measurement of the two α breakup fragments from the projectile-like ground-state ⁸Be in the ¹²C+²⁰⁹Bi reaction. The experimental information of the relative energy E_rel, opening angle θ₁₂ and breakup direction angle β of the two α was kinematically reconstructed. The obtained results align well with the asymptotic breakup behavior of the long-lifetime ground-state ⁸Be. This study successfully reconstructed the properties of the long-lifetime breakup nucleus, providing groundwork for future investigation of the breakup of nuclei with short-lifetime and underlying reaction mechanisms.