Z = 6 magicity in 15C and 14B revealed by the 2H (15C, 3He)14B reaction

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A new measurement of the 2 H( 15 C, 3 He) 14 B reaction was conducted to investigate proton shell evolution in neutron-rich carbon and boron isotopes. The experiment employed a radioactive beam of 15 C with a higher energy at 28.3 MeV/u and a large acceptance charged particle detector array LACPU, enabling coincident measurement of high-lying unbound states in 14 B that include π 0 p 1/2 - π 0 p 3/2 transitions. A newly observed 3.45(35)-MeV resonance with a statistical significance of 3.1 σ in 14 B exhibits π 0 p 1/2 - rather than π 0 p 3/2 -dominant character according to structural model predictions. The extracted proton spectroscopic factor of 0.16 ± 0.06 for 15 C g . s . not only follows the systematic decreasing trend in neutron-rich carbon isotopes but also agrees with theoretical predictions, providing clear evidence for the Z = 6 magicity in 15 C. Furthermore, systematic analysis of the energy splitting between the π 0 p 3/2 and π 0 p 1/2 orbitals in 12 − 14 B reinforces the robustness of this magic number in neutron-rich nuclei systems.