Explanation for spectroscopic factor quenching in knockout reactions

The systematic quenching of spectroscopic factors in terms of separation energy asymmetry in single-nucleon knockout reactions remains a puzzle for two decades.We propose a core screening effect due to a finite-sized probe, considering the suppression when deeply bound nucleons in the projectile nucleus are removed bythe heavy-ion target.The core screening effect is simulated as a medium modification of single-particle wave functions inside the projectile.This work shows that the parameterized screening effect can explain the isospin dependence of quenching factors,offering insights into reaction mechanisms between two composite quantum systems.